I was attacking a sorcery node filled with air elementals. But they are invisible and didn't attack my units, so I was just forced to flee. What solution is there to this problem?

I am playing Community Patch

In this instance, it sounds like Flying is the main problem you need to overcome, not Invisibility. Invisibility is going to make it harder, since it will prevent most of your ranged units from attacking at actual range, but it is the Flying ability that has the Air Elementals not engage your walking troops.

Bring things that can engage flyers. Barbarian troops, especially Berserkers, should work. The various units with Gaze attacks (like Basilisks) may be useful. Flyers of your own may work, like Griffins. Aim to have magic weapons on any normal units that you send into the node to overcome Weapon Immunity.

Bookwyrm's right as always, the flight is the real issue.

But as to invisibility, including any undead unit in your stack will let you see where your opponents are. Not necessarily an option, but if you have access to undead it's a sometimes-overlooked solution to at least finding your targets (and hitting them with square-targeting magic).

Of all the Sorcery creatures, only the Skydrake can detect invisible creatures; and extend that awareness to all remaining sorcery based creatures.
Otherwise, if you can either start the game with Life Books, or get one or more Life books out of certain random {but tough} lairs, you can acquire the spell 'True Sight' in order to see invisible creatures.
The Life Creature 'Archangel' can use this spell against you.
Use Hero's and Champion's! They need a ludicrous number of XP's, so never use anything else to clear a lair/node; use them with regular troops only when defending a city.
When Malleus gets tough enough, he casts 'Flamestrike' which damages every opponent.
Web will put them on the ground and make them easier to hit and unable to attack until they break out of the web (they can still defend).
Running up and hitting them works. A hero with a decent set of armor, a weapon, and be working on its second level of rings (XP's) should survive.
Running up and then instead of hitting, using Bookwyrm's advice works very well.
DON'T run up and hit them. Every time something gets melee attacked, it hits back! If you're shooting them, or casting spells, they can't hit back.

A Few Hints:
There is a sorcery spell that Unsummons and almost always one of your opponents will have that spell. Your 'Summoned Champion' goes bye bye. Use only hero's and champion's that offer to join you.

Recommended 6 Hero's and Champion's:
The only hitter I have is either Fang or ???-evil paladin whose name escapes me at this moment..
My only primary spell caster is Malleus.
My two non-spellcasting Bowmen are Shuri and B'shan.
My two spellcasting Bowmen are Marcus and Allora.
Note: Almost always on the turn or within two turns of acquiring 100gp, a Hero will offer to join you. Save before this happens, and try-try-again.

The number of figures in the group is the number of attackers. So eight Halfling Swordsmen that attack at 4 (8X4=32) vs four Gnoll Wolfriders that attack at 6 (4X6=24) means the Wolfriders may kill four to six Swordsmen, but aren't likely to survive.
Since the Warlord Bonus is for every figure in every one of your troops, a Warlord's first level troops will sometimes be able to beat elite troops of the same kind if the opponent isn't a Warlord.
On rare occasion a Warlord will have to build troops before their Alchemists Guild has been built {usually to protect conquered cities).

Two Recommended (must have) Skills:
Warlord:
For reasons just detailed above.
Artificer:
You can Enchant An Item or Create Artifact for half price and break that item for double the amount of mana returned for what it cost you to make. 38-88-200-413 In just four castings you can be breaking an 'enchanted item' that returns over 800 mana points. That means you can put all the mana you make in other ways into casting skill (unless you don't have a library yet). It also means when you do two-for-one, you can make many artifacts for all your Hero's.

Halfling's are the most advantageous race, followed by Highmen.

Enemy shooters will almost always shoot at your weakest troops first. When possible, my two weakest troops are {regenerative} Troll Shaman.

Save and reload often. Combat is random; unless the odds are overwhelmingly against you, or your opponent, the underdog can win. New spells are random too.

Exploit:
When creating an Artifact - Weapon for your Hero(s), start by making a staff and giving it the ability to cast one spell four times. (IE: Doom Bolt, Web, Phantom Warriors, or Mass Healing). Change your mind and give that staff a different ability instead. Then either keep the staff or change to the weapon you really want. Your new weapon will be able to cast the spell you chose 4X. Also, with its 'instant kill' ability, 'Stoning" is a must for every weapon except for Malleus's.
BTW. This exploit can be used for any item you make, but experience has shown me that sometimes the game won't allow two of these items to work together and may even make neither/all of them unable to cast spells.

More if you want.

"There is a sorcery spell that Unsummons and almost always one of your opponents will have that spell. Your 'Summoned Champion' goes bye bye. Use only hero's and champion's that offer to join you. "

Fortunately, that's not how that works. Heroes hired from the summon spells are still "normal" heroes.
However heroes can be hit by that spell if they were transformed into a fantastic unit by another spell - Chaos Channels, and Black Channels do it permanently, and in Caster of Magic Mystic Surge and Raise Dead do it for one battle. The Incarnation hero is special, it always counts as a Life creature during battle but only during battle in all versions of the game.

Actually, that is how it works. Hero's get a saving throw, and so do magic spirits or anything else that is summoned. The tougher the summoned creature the better the save, but if the fail saves, any summoned creature disappears.

BTW I may be talking about apples and not oranges. Everything I've said applies to the original, but patched, version of the game. If 'community patch' changes things I'm not aware of, I apologize to all.

I have commentary, and some things here seem to be incorrect. Sky Drakes have Illusions Immunity, so they can see invisible creatures. As their controller, they also let you see the invisible creatures, but they do NOT extend this to other creatures on your side, whether or not your other stacked units are Sorcery creatures. For example, having an allied Sky Drake present will not allow Storm Giants to target invisible creatures at range. Feel free to include heroes (and champions, which are just elite heroes), but don't feel like you need to send in a stack of heroes without support.

When a battle ends, every surviving unit on the winning side that is eligible to earn XP will earn full XP for the battle (2 points per enemy unit killed, iirc). Creatures with Regeneration count as survivors, so feel free to let your trolls suicide into the enemy as long as the rest of your army can successfully mop up. Not all units are eligible to receive XP; fantastic creatures (except Torin) can't level, and normal units can only get a total of 120XP (granting Elite rank). I believe Black and Chaos Channeled units have some issues gaining additional XP, but I don't remember the specifics. In order to run up and hit them, the hero (or any other unit) will need to be able to initiate an attack on flyers. Having a thrown weapon (Bagthru, Gunther, barbarian units), breath weapon (fire or lightning) (Fang, Hell Hounds, one of the possible effects of Chaos Channels), flying (Fang, but NOT Jaer (who has wind walking), draconian units), or a gaze attack (Chaos Spawn, Basilisk) are all methods of initiating a melee exchange with a flying unit. There might be some others I don't recall at the moment.

If they don't have a way to initiate, then they can't just run up and hit the air elemental. Torin is both mighty and completely unable to kill an Air Elemental unless he gets some help from something else (like spells that you know) or the AE suicides on him. This sounds incorrect, since heroes aren't fantastic creatures and Great Unsummoning targets fantastic creatures. Torin is the one hero exception, being a fantastic creature of Life, but his magic immunity would block the spell even if he didn't have absurdly high resistance.

What is your source for this claim? Shuri is a pretty decent hero for her tier, and she has good accuracy because of her Blademaster ability.

In my experience, B'shan is basically only useful for the +10 gold per turn. He has low attack, low defense and hp, and he isn't accurate. Sure, a lot of items and experience can make him powerful, but the same experience and quality of items would make any hero powerful and most start quite a bit stronger. This isn't true.

Each turn, there is a chance a hero will approach and join you. Your fame and the number of heroes you already have influence this chance, but not your current gold total.

That said, if the "hero offers to join" chance is successfully rolled, their (normal) offering price is checked against your current gold total before you ever see them. If you don't have enough gold, then they still don't make the offer. Be aware that the price reduction from Charismatic isn't used for the "hero cost versus current gold" check. If you have 75 gold and Charismatic, a hero that normally costs 100 gold won't appear even though with Charismatic they would only ask for 50 gold on the "Hero offers to join" screen. Combat is a lot more complicated than this implies.

The wolf rider shields apply against each of the 8 attacks from the swordsmen. This is why spearmen are generally so awful in combat; sure, lots of figures mean they make lots of swings, but each swing is very weak and unlikely to penetrate the target's defense. The wolf riders are using stronger attacks which are much more likely to penetrate the swordsman defense score. Unless the swords get lucky early in the fight, the wolf riders are very likely to win because the swordsmen lose effectiveness a lot faster as figures die.

This match up is a little misleading though, because the Lucky ability skews the numbers in a lot of ways. Experience level also factors in heavily; the extra stats from higher experience helps the more numerous swords more than it helps the wolf riders. Warlord just increases the experience level of all your non-fantastic units by one, including above the normal maximum if the unit has enough experience. This closes the level gap between Elite and non-Elite.

That said, the stat gains from increased experience levels are pretty significant which makes Warlord a strong ability. This is opinion, and depends heavily on what you want from a race.

Halflings are a good race for a lot of different things, but "best" depends on what you want. For example, if you want lots of magic power and spell research, halflings are only middle tier. This is also a matter of opinion, and I disagree strongly.

Stoning can only kill one figure per exchange, it only works on the attack type(s) the weapon affects, and the target has to fail a resistance roll for it to work. Any unit this is likely to affect probably isn't a big concern for the hero, and the strong targets are more likely to shrug it off.

I'd suggest spending the 150 mana and casting skill on more generally useful weapon abilities, like extra Attack or To Hit, or even just pocket the cost and get the weapon to the hero faster.

I've always fiddled with this and wondered about the results: How do you best equip an archer hero? A lot of the magic effects sound wonderful, but in practice only affect melee. Is the best you can do just adding attack and to-hit? Or is there an effect or two to make my bowman more powerful?

Giving your hero +6 attack, +3 To Hit, +3 defense, and +10 casting skill isn't good enough for you? :D

Phantasmal and Lightning will both help punch through high armor values, Haste will double the number of attacks made per shot (which sadly means the hero can only shoot for 4 rounds before running out of ammo, but apparently Haste also helps melee attacks), and Magic Immunity is useful protection. If your archer is very inaccurate, then Chaos can help (halves attack value, but makes it Doom damage for unreduceable auto-hit damage).

The main disadvantage of a bow is that it primarily doesn't help the hero's melee attacks, so that +6 attack won't assist their counter attacks if something gets into melee or if they run out of arrows.

Part One:
In my replies, I may use the word “you”. That word is intended to mean ‘you-the-player/reader’ and not specifically you Bookwyrm627 unless otherwise stated.

Before I respond to anyone further, I do apologize. I mixed useful fact with personal opinion and/or play-style, and didn’t always clearly state which was which. I also didn’t state a few things clearly enough because “I” knew what “I” was saying. Again I apologize and I’ll endeavor to do better (no guarantees).

Note:
In the past two decades I’ve almost always played using:
1. Impossible Difficulty; Three (3) Opponents; Small or Medium Land Size; Powerful Magic
2. Custom Game. Although it doesn’t matter what character you choose to play, during the first year I had this game I always seemed to lose most frequently to Oberic. For that reason, it is force of habit for me to choose to play him in a ‘Custom’ game.
3. Two (2) books each in Chaos, Nature, and Sorcery; Warlord; Node Mastery; Runemaster; Artificer.
4. Eldritch Weapon; Walk on Water; Word of Recall.
5. Halfling; Banner/Flag-color.

I’m also one of those people who saves and re-loads their game until the results of capturing a City/Dungeon are satisfactory.
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Bookwyrm627, one of your complaints about the veracity of my statements was about Hero's just running up and hitting Invisible Creatures they encounter in combat. If Hero’s cannot hit flying creatures normally, I’ve forgotten that is so, and I readily admit I could be wrong.
In fact, it is entirely likely that anything I have to say may not always be true for other setups or choices.
For example, in my experience, I've found that a weapon with the ‘Stoning’ Ability can hit anything including flying creatures. A Hero may not hit as often or as hard, but it can hit.
As an Artificer who makes, and usually breaks, items/artifacts for the first half of the game, because of its ‘instant kill’ property, having a weapon with ‘Stoning’ is both inevitable and likely for me. Then, if my Hero is of Champion level or higher, my Hero will sometimes hit a flying creature.
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Bookwyrm627, you also pointed out that "Sky Drakes have Illusions Immunity, so they can see invisible creatures. As their controller, they also let you see the invisible creatures, but they do NOT extend this to other creatures on your side, whether or not your other stacked units are Sorcery creatures. For example, having an allied Sky Drake present will not allow Storm Giants to target invisible creatures at range."

Since I avoid summoning anything if I can, Bookwyrm627 it's likely you're right about what a summoned Sky Drake can do for you.
As for the rest, I apologize, I didn’t state things clearly/correctly.
Enemy Sorcery units in a Node with one or more Sky Drakes not under a Wizard’s command, will advance and attack. Kill all the Sky Drakes and all the other Sorcery units stop knowing where your Hero’s/troops are unless they are standing beside them.
Bookwyrm627, are also right about 'Ranged Attacks’. Nothing that isn’t Immune to Illusion, or which hasn’t had the ‘True Seeing’ spell cast on them, can do a ranged attack upon an invisible creature.
{Area effect spells still work normally.}
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When I admonished people to never user normal troops except for defense; and always use Hero's for clearing Dungeons, Bookwyrm627 responded by saying "Feel free to include heroes (and champions, which are just elite heroes), but don't feel like you need to send in a stack of heroes without support."

{{
About Champions [troops] & Champions [Hero’s]:
1. The Life Spell ‘Crusade’ + Warlord equals normal troops that achieve Champion level. Compared to normal Champions, normal Elites are half way down the scale.
2. The other kind of Champion, could be thought of as an ‘Improved Hero’; but Bookwyrm627's ‘elite hero’ is equally accurate.
}}
Shuri, Markus, and several other Hero's, have the ‘Pathfinding’ Ability which doubles movement over all Terrain Types and even through the air; provided that at least one 'Pathfinder' is not flying.
Without anything special going on, Shuri can travel four spaces. But not if she is with a troop that only moves one space and therefore limits her movement to two spaces.
Shuri and her fellow Hero's can also be equipped with items that increase movement.
An 'Enchanted Misc Item' can increase movement by +2; or +4 for anyone under the influence of 'Pathfinding’. So if Shuri and her fellows are wearing something with +2 Movement, then they can travel 8 spaces per turn.
An Artifact with 'Endurance' and +3 Movement winds up being a +8 Movement bonus with 'Pathfinding’ and allowing Shuri and friends equivalently equipped to travel 12 spaces.
With the right Artifact(s) plus ‘Endurance’ in spell or Artifact form, Shuri and her fellows could travel a maximum of 18 spaces. Add Flight, and her fellow Hero's could travel one step beyond where Shuri can take them.
But in all cases, if you bring a Swordsman without the ‘Endurance’ Spell cast on it, you'll only move two spaces.
In a race to get to lairs/towers/nodes before your opponent, bringing normal units which limit your movement to two or four spaces is giving your opponents an unfair advantage (and they get to cheat anyways).
So I didn't say you can't use normal troops, I just didn't go into detail about why you should never use them unless they happen to be in a city you're defending.
{An exception to this is if I have no Hero’s, and at the beginning of the game I find out there is another city too close to mine. I’ll attack without Hero’s.}
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Bookwyrm627, I made an incorrect statement about combat and XP's to which you replied " When a battle ends, every surviving unit on the winning side that is eligible to earn XP will earn full XP for the battle (2 points per enemy unit killed, iirc). Creatures with Regeneration count as survivors, so feel free to let your trolls suicide into the enemy as long as the rest of your army can successfully mop up. Not all units are eligible to receive XP; fantastic creatures (except Torin) can't level, and normal units can only get a total of 120XP (granting Elite rank). I believe Black and Chaos Channeled units have some issues gaining additional XP, but I don't remember the specifics."

A long time ago one of the programmers of this game posted a list of random ranges, charts, and calculations/formulas to explain how the combat Attack/Defend System worked. That programmer also stated that XP's are not divided, but summed and given equally. So yes, my explanation of how combat works isn't even close to the reality.
With that said, and in response to other comments about combat:
A. If Shuri and the troops with her take four turns to get to a Dungeon, it may not be there any more because an opponent got there first. But if Shuri and her fellow Hero's can get to that same Dungeon in one turn, it is there.
Subjectively, every time I mix Hero's and normal troops it just takes forever for my Hero's to gain a level because they are spending so much time traveling.
Objectively, since my opponent is getting to these Dungeons before me, my Hero’s aren’t earning all the XP’s they might otherwise.
I therefore always recommend people to not attack anything with slow troops which cannot gain as many experience levels as their Hero's.
B. Some units are not meant for Attack! Spearmen in particular have a great 'Defense' which kills most enemies quite effectively. Especially if they have Terrain Defense Bonuses and/or defensive/offensive spells on their side.
C. A 'Thrown Attack’ is only possible before melee begins. Since, in melee, everything can hit back while defending, and since Sky Drakes have such a great defense, I recommend ranged attacks before thrown/melee whenever possible.
D. About hitting flying creatures... if you cannot 'ground' the flying creature using 'Web', you will need ranged weapons; thrown weapons; flying troops; Fang; the 'Flight' spell; any/many of the numerous ‘damage’ spells; a Hero equipped with a weapon which has the ‘Stoning’ ability; and anything else I may have forgotten.
{Lots of 'casting skill' really helps in those situations.}
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BTW. I do have more replies and responses, but the software editing program for this forum finds all my replies/responses to be too long (ahem, I mean too long for one post). But it won't let me post these replies/responses in two parts and crashes when it tries to join them. If someone else responds after this first part, I'll post the second part.

It supposedly only tries to join posts if the time difference between posts is very low. I dont know the exact number of minutes though.

This might be a point where we're talking about slightly different things. A weapon with the 'Stoning' ability does not give a walking hero the ability to initiate a melee exchange with a flying unit. Initiating a melee exchange requires some way of 'reaching' the flyer (gaze attack, flying, thrown, etc)

If a flying unit attacks a walking unit, the walking unit will counter-attack the flyer, and in the base game defenders will always attack even if they could win by simply running out the 50 turn timer.

What units to stack, and how fast they move, are strategic considerations that need to be made. Being able to move farther each turn is definitely an advantage.

High level heroes do tend to be powerful, especially when backed by a Runemaster+Artificer wizard, but sometimes you just work with what you have. Sometimes a hero will fare better when accompanied by a stack because there are other units to provide damage, even if they can't use their full move allowance to do so, like Valana leading a stack of pikemen.

Halflings completely lack any form of fast unit, which is one of their drawbacks.

I suggest you try Nomads (horsebowmen) or Gnolls (wolf riders). Both units have low building requirements, both have speed that is comparable (or better!) than the default hero movement, and both units are pretty solid combat units in my experience. They can help you start expanding long before you have a stack of tricked out heroes. Gnolls need to be aggressive and conquer some other races to access infrastructure, but wolf riders are an excellent mix of fast, powerful, and expendable. Nomads are pretty good at infrastructure already, so they aren't as dependent on conquering other races.

Make the (good) normal troops, use the troops, love the troops. You say you usually take Warlord, which is designed to buff normal troops. :)

Some troops aren't very good choices (looking at you, Mammoths), but most races have at least one good option. These can begin conquest before you have any heroes at all.

Spearmen have some of the lowest stats in the game, including defense. They use their Attack value when counter-attacking something that hits them. Warlord might be skewing your perception of them some. I do like to use them as town garrisons so I can cast spells, though.

There is no such thing as a Terrain Defense Bonus. I'm not sure what you're referencing here.

There is a character limit per post (10,000? I don't remember offhand).

If the same person posts twice in a row within 10 minutes, the forum software tries to merge the posts. Next time, wait 10 or 11 minutes then try posting again.

In response to your questions about bows/archer-Hero's... the only two troop enhancing combat spells that I can think of at this moment which require Melee Combat instead of Combat are Immolation and Cloak of Fear.
Combat spells like Eldritch Weapon and Flame Blade stack and do exceptional damage. Giant Strength adds +1 to all combat Attack Rolls. The list goes on and covers just about every spell that adds to a troop's or Hero's combat abilities.
Bless, Flaming, Stoning, Lightning, Death, Holy Avenger... well, there's a lot of Spell Effects which can be added to a Hero's weapon which will make it more deadly even if you don't use the ‘exploit’ to give your weapon spell charges.
But heed Bookwyrm627's warning about Haste. Unless your Hero dies, melee attacks are unlimited; but you only get 8 bow shots (applies to all physical Ranged Attacks). You don't want to waste two shots killing a ghoul that can be killed in one.
With that said, any bow used in melee combat still gets its Spell Effect Damage added to the Hero’s normal attack damage. So in most cases the spell Warp Wood or running out of arrows is just an inconvenience.
But if you use the ‘exploit’, you can consider putting Phantom Beast in your weapon and having four of them (summoned one-at-a-time) fighting on your side. Warp Lightning, Flame Strike, and Doom Bolt are awesome too. There are a lot of possibilities depending upon which spells you have and/or can trade for.
Also, for reasons I'm not quite certain about, Fang, and that evil Paladin whose name I still can't remember, are almost immune to physical damage from any creature with a lower Attack than theirs. That's why my optimal party of Hero's always includes one of those two melee fighters.

PS: Because I almost always play the game with so few Spell Books, Spell Effects like ‘Phantasmal’ or ‘Lightning’ are usually not available.
1. My Artifact Bows are almost always Flaming, Stoning, +6 Attack, +3 to Hit & 4X Spell.
2. The only Artifact Axe I make has Flaming, Stoning, +6 Attack, +2 to Hit & 4X Spell.
3. Malleus's Artifact Staff is +6 Attack, +3 to Hit, +20 Spell Skill, -4 Spell Save & 4X Spell.
Since each weapon uses the 4X spell 'exploit', my six (6) spell options are awesome and I may actually use different spells in each weapon.
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I believe that most of the spells you listed do not affect missile fire. I presume that they do come into effect when your bowman goes into melee (at least I hope so). But by 8 rounds into a battle, I would prefer to be about done. And in that time I would prefer to keep the bowman out of melee.

Edit: I should probably mention that my primary experience and knowledge is with the base 1.31 game. The Community Patch is probably very similar, but I can't speak for changes made by Caster of Magic.
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As far as spells, some spells help ranged attacks, but quite a few don't. For example, Giant Strength only buffs melee attack, not ranged attacks of any sort.

Most of the spell effects that can be added to a bow will help the bow's ranged attack (not melee attacks), but Flaming is apparently one exception. It gives a bonus to melee without buffing the arrows.

Nope. Most of the bow's effects only help the hero's ranged attack, not their melee attack.

This is probably because you're used to tricked out heroes, and both of these heroes can deal damage to the enemy before the enemy gets their counter attack.

Fang has Fire Breath, and because he's flying he probably gets to use it most of the time (melee walkers usually can't initiate an exchange on him).

Gunther, Bagthru, and Shalla (especially Shalla) can all perform somewhat similarly if they initiate a melee exchange, since they have thrown weapons. Gunther and Bagthru are closer to glass cannons, relying on their thrown attacks to kill the enemy to reduce incoming damage.

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Mortu is special, being one of the Champion tier heroes that is built for destroying targets via melee.

Mortu has first strike, so when he swings, he gets to deal his blademaster+might damage to the armor pierced enemy before they can retaliate (assuming the victim doesn't have "Negate First Strike"). As an example, lets consider a Mortu with 200xp (Champion level) with non-combat random abilities. Looking at the wiki listing, he's got 18 attack at 60% accuracy without any equipment. That's an average of 10 damage per swing before the enemy counters. Bump him up a level (to Lord) via warlord or another 100xp, and he's sitting on 20 attack with 80% accuracy (16 damage per exchange on average). Give Lord Mortu an axe with +6 attack and +2 To Hit, and you're looking at 26 damage per exchange. Let's pit him against some units! Listed values will use their defense after Mortu's armor piercing is considered.

Remember that each point of defense represents a 30% chance to block a single point of damage, and damage is blocked on a per-figure basis. So the first figure uses their shields to block damage, then loses hp, then when it dies the next figure steps up and uses its full shield count, loses hp, etc. Rinse and repeat until all damage is handled or the defending unit dies.

-Anything that can't negate his First Strike (ex. pikemen) and has less than 26 points in combined def and hp will just die. We're only going to look at Elite normal units here, since they have +1 hp per figure; most units that are Veteran or below simply don't have the stats to survive. If they don't survive, they can't counter-attack.

-Elite Dragon Turtle (5 def + 16 hp = 21 total) just dies.
-Elite Stag Beetle (4 def + 21 hp = 25 total) just dies.
-Elite Berserkers (2 def + 4 hp = 6/figure, 12 def, 24hp total) can have 2 figures left alive if at least 7 of their 10 shields successfully block damage. They need to block with at least 3 of their 12 shields or the entire unit just dies.
-Elite Paladins (4 def + 5 hp = 9/figure, 16def, 20hp total) can have 2 figures survive if they block with all 12 of their shields. They must block at least 7 of 16 points of damage with their defense or the entire unit is dead.
-Elite Javelineers (3 def + 3 hp = 6/figure, 18def, 18hp total) can have 2 figures survive if they block 12 damage with their 15 shields. Block with at least 9 of 18 shields or die.
-Elite Minotaurs (3 def + 13 hp = 16/figure, 32 total) need to block with at least 1 of 6 shields or just die.
-Elite War Trolls (3 def + 6 hp = 9/figure, 36 total) need to block with 9 of 9 shields to have 2 figures survive, or 3 of 12 shields to have 1 figure survive.
-Elite Hammerhands (3 def + 5 hp = 8/figure, 48 total) can have 3 figures survive if they block with 7 of 12 shields. They'll always have at least 1 figure survive a single exchange with our Mortu, and they might be the only normal unit with enough hp to do so.

What about Fantastic Creatures?
-Archangel (23 total) dies. Unicorns (24 total) also die.
-Stone Giant (24) dies. The other Rare and Very Rare Nature creatures have piles of hp, so they can survive at least one exchange. You're looking at Behemoths and Great Wyrms (45hp each) to guarantee survival through two exchanges. Basilisks get a mention for 30 hp on an Uncommon summon.
-Sky Drake needs to block with 2 of 5 shields or die. Even in a Sorcery Node, no other Sorcery creature has the def + hp total necessary.
-Gargoyles could survive if they block with 12 of 16 shields.
-Chimeras (32), Hydras (90), and Great Drakes (30) have the hp to survive a hit.
-Zombies need to block with 9 of 18 shields. Shadow Demons need to block with 7 of 8 shields.
-Werewolves (30), Wraiths (32), and Death Knights (32) can all survive a hit.
-The Demon Lord doesn't have the raw health and shields to survive, and Mortu's Magic Immunity prevents its Life Steal from having any chance of helping it.

The now-damaged opponent (especially if they are a multi-figure unit) still has to break through Mortu's 8 defense before they can actually deal any damage. Remember that all this is just a mid-level Mortu who only has a +6/+2 axe, no other items or enchantments!

Roland has a very similar ability set to Mortu, so you should see similar results with him as well.