This allows you to deal full damage to units with Physical Protection or Physical Immunity, such as Nordic Glows, Wraiths or units protected by the Liquid Form enchantment. As long as they don't have Magic protection or magic immunity.

The Weaknesses Bookwyrm mentions were only introduced in AoW2.

Damage is done according to whichever of the attacker's Strike elements is least opposed by the defender's Protection or Immunity Elements. So if you have fire strike, cold strike, holy strike, and (physical) Strike, then you'll do full damage to a Wraith which is immune to all of those except holy. Immunity also prevents special statuses like Poisoned (poison), Stunned (Lightning) etc.

Heroes consist of the basic chassis for their hero type and race, plus their personal extra stuff. Strike is in the chassis so it's not possible to remove for a specific hero. You could mod it out of the chassis, but then you'd have to manually re-add it to every hero you wanted to still have it - not at all worth the effort, and would only work with that mod.

However the infantry heroes, which are not seen ingame but can be resurrected and used in unmodded game with scenario editor tricks, don't have Strike in their chassis. I believe that they can still hit things if they get a weapon item because those all tacitly have Strike.

I may be using this in future maps I make, but sadly I don't want to boast about future projects because I am unfortunately not a NEET any more and mapmaking is a very slow process because of things like naming the towns and so on, which I insist on doing with a racial naming rubrick, and because I want to finish my item set first (more than half done now). Swirlmount needs an editing pass too.

OK, it's "Strike" not "attack".

So for the mace, do I have to select one or the other, or are both enabled by defualt.

This is what it looks like. Only one is highlighted.

Free movement dispelled doesn't kill the unit in AoW1, it makes them like a building where an opponent can capture the unit (with the exception of firehalo-boats on "reserved" terrain where the Crushed! trigger genuinely kills them)
You can make a specific strikeless hero in aow1 without modding, you are just limited to the three basic body models unless you mod.

Both are enabled by default

I haven't been able to figure out what the highlighting means, if anything.

All the abilities on the item are applied to the hero using it. Some items need to be equipped, like helmets, but some can't be equipped and only need to be in the hero's inventory, like wands.

You can compare the differences by equipping/removing the item and checking the hero ability list. Extra abilities and their source will be listed (though a given ability will only be listed once).

I really need to try this out.

But how? https://i.imgur.com/O22EU8t.png
It's greyed out, can't delete it.

Huh. I've actually had no luck dispelling spells on enemy units; the game won't let me cast dispel magic on them overland. Can it only be done in combat?

How good is First Strike.

Given the option of starting level 4 with:

+1 ATT wepon, +1 DEF helmet, +1 DEF shield, halfling hero

or

+1 ATT wepon with First Strike, + DEF helmet, centaur unit

In essence taking a hero and a shield for First Strike and centaur. Which would you chose? I'm leaning for the hero but First Strike sounds really good.

If you indirectly remove the spell (remove your own spell, defeat the source leader, disband) you'll see the "stranding" effect where units act like stationary structures. If you dispel freemovement during a mountaintop battle and then retreat (or lose), you will see a spawn check where the unit gets placed on the nearest valid hex (magically reappears at a different hex after battle).

First Strike + Hero, ditching the helmet and unit. No contest. If you are still very early in the campaign (I'm guessing North Trade Route?), I might place preference on the First Strike weapon over the hero. Both could possibly be replaced, but you're more guaranteed to run into another hero which you can then feed experience than you are to run across another first strike weapon. You will come across another hero later, but you'll have to be diligent in clearing those caves and ruins to get the chance to find another first strike weapon.

If your leader is combat oriented, which he should be, then First strike can let him charge into a group of swordsmen and kill them via retaliation without them ever getting a chance to swing.

First Strike means you retaliate first, before the attacker gets to swing. If the attacker also has First Strike, then their first strike will trump yours (so goblin spears would still swing first if they attack you).
So you can't dispel an enemy's buff spells overland? Dispel Magic is combat only then, which means it won't be of any use in player vs player battles, with Disjunction for removing globals.

Guess one doesn't have to worry about losing water walk/etc while over hostile terrain then.

It's a trick with the mountless heroes (pic attached). I think you can still change their body type after creating them (haven't tested that yet)

That's not an option.

North trade pass gave me the hero, Caverns gave me First Strike.

First Strike is what I'll take then.

Ah. Definitely first strike, then. You'll pick up either a lizard or dwarf hero soon enough.

If you start on the surface, select build road and then make your builder go underground on top of inverted terrain (surface terrain placed in the underground), you can produce roads underground during the game.

I've seen inverted terrain has been mentioned multiple times. What is it? Surface terrain on a nonsurface layer?