For even the possibility of getting the future installments for a fair price, I've decided to write this guide.

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RANT STARTS HERE

Btw, their marketing department rly need a kick, as the text for the bundle is very misleading. 140 bucks is the current price, and that'd include BoD too, which I've already have, but I'd be ready to pay, even with the whole project might not come to fruition.
The problem with the whole bundle is:
a) it is not even on Steam, but their own website
b) it does not tell you it is Steam-exclusive, but that "it is available on all platform Steam is available on", and that eg. means PC, what GoG runs on to start with, so I assumed as BoD is on GoG, and is on PC, the bundle also applies to GoG. Turns out it is not (at the moment), and be sure as heck, I won't pay, considering inflation, many times over this 140$ limit (like 500$ if the games come out every 2-3 years).
c) they do the usual advertisement "we are small company, we need crowed-funding money" - but somehow they limit themselves to a single shop, instead of the mass-market.
This whole thing sounds stupid, or that's just me?

It really feels like Steam is paying decelopers extra for exclusive contents, and in my eyes that just makes that company horrid. (On the sidenote my even bigger issue with Steam is, their advertisements are onboctious, and their "gog-galaxy equivalent" eats a whole lot of computer-resources, so I could run even less games/programs at them.)

But onto the game.

RANT ENDS HERE

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So, you start with the Knight, and you have to reach clvl 5 to unlock the other two classes. Don't bother with those yet.

You start in the Tutorial Dungeon. This is unskippable, but it's not a big deal, and it's actualy perfectly fine. Be prepared though, that you'll likely die at the first boss because all the popups of tutorial messages. This seems to be some kinda proper way to intruduce the resurrection/continue mechanic, but still annoying.
Completing the Tutorial Dungeon unlocks the Flexiscope feature, which means you can set how far you want to progress, making it a 2% progress in 5 minutes, or 12% progress in 50. On the sidenote though, shorter settings give you much less resources (projected to progress-percentage), and believe me, you want resources.

You can start a game on 3 settings: 1) casual 2) normal (less healing, leaderboards) 3) roguelike (no free healing/respawning in town, can't change to the other settings).
I suggest you start on Casual. and after the tutorial dungeon set to Very Small dungeons/sessions. This is because you want for 5 dungeons (or dungeon levels - all dungeon consists multiple levels -, I forgot) where you go straight from entrance to exit. This means no manouvering around too! Do not go back on your tracks even one step!

With that delt with, you might want to continue with this character, for exactly 20 dungeons (not dungeon levels, and it must be the very same character). Still stick with the Very Small Dungeon setting to make you life easier, because Big setting will be 10+% progress every time, so reaching 20 Dungeons would be playing through the game twice. And the bottom level is actualy a whole harder experience anyway.
Achievement-progress is not cumulative between characters! Once you unlocked an achievement you have that for your main account though, so no worry.

With this out of the way, you might want to start a new character, still on Casual setting, and this time play through the whole main story with 2 things in mind: never ever purchase the Cauldron (extra stats or whatever), and never ever die. You can of course try to keep playing with your first if you feel like that.
The tricky part can come on the very bottom level (fighting Not-Diablo), where whole bunch of enemies will teleport on your head. You have been warned.

One problem is, all the cards you get is random (so you won't get all cards in the main story part), and the resources are very limited in the main story, so you definitely won't be able to use all features during this, and you can spend resources on a bunch of things, like: unlocking card slots, recharging supplies, improving cards, fusing runes, and a bunch of other stuff you won't even be able to unlock in the main story part (like refilling Death Rage).
Now how it works is, after beating Not-Diablo, you unlock Freeplay Mode.

In Freeplay Mode you can choose what dungeon-type you want to play in from the three section of the descent (I strongly suggest to not pick Hell unless you want a harder challenge).
You also get 4 difficulty-settings: 1) Standard, 2) Hard, 3) Nightmare, 4) Massacre.
Iinitialy you can't choose, they must all be unlocked by playing on the lower difficulties.
After choosing the difficulty, you still get the familiar Flexiscope setting. I feel the easiest option here will be the Small dungeon. Here ther game also tells some progress-precentages, so I assume this is a shorter version of the main story dungeoncrawling, and completing a difficulty fully unlocks the next difficult.

Beating the story mode once also unlocks widerFlexiscope-options for all the other characters.

NOTE ON EQUIPMENT:
For Causal setting, main story mode, you can get away using only passive equipment-cards. Pray that you get the boots with Knight, it helps immensly. Other good stuffs are the shield (avoid 33% projectiles), and the doubleslash, and extra elemental damage. the rest is up to you, but try to keep in mind some potions, namely the healing potion, and the invincibility potion (this later for the bottom part for the head-porting mobs).

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Now onto cosmetic unlockables.

I don't know how Avatars work, but they have their separate menu (cogwheel on the avatar-picutre). This choice of avatars applies to your main account.
How I think it works is, your character exp, and achievements give you the points to ulock more.

On to (further) achievements:
- most of them unlock naturaly, by grinding/playing the game
- don't forget to keep using the bombs for the Knight, the special arrows for the Archer, and the golems for the Mage as soon as you find them. The bomb cards throw bombs for a period. The arrows work a bit differently: it gives you supplies of arrows you can shoot if you have the proper card equipped. These arrows get on the top you have "locked" inside the cards. The "unlocked" arrows' maximum is 99. No data on golems for now.
- try to have equipment that spawns HP/MP for you, as that is achievement-related business too.
- keep grabbing (preventing) enemy abilití-icons charging, that's achievement too.
- oh, no note: if a golden achievemnt is "do stuff 500 times", then it is 500 times, not 5 + 50 + 500 times considering the lower grade achievements.
This actualy leads to a BUGGY BEHAVIOUR, where the "unlock all Silver/Gold achievement" percentages do not show up until you unlock all Bronze/Silver achievements.

Mind-bending achievements:
- destroy X monsters in Y second: no advice here
- finish a big game on X difficulty receiving all the badges, aka. clear named dungeon, also do not perish.
- finish a big game on massacre difficulty w/o equipping any cards, and no source of healing (I expect dying here a lot, so don't play roguelike, as resurrection costs cois there, also empty the cauldron first)
- Master all quests: this means buying/finding golden keys, and bashing the bosses on their own higher difficulty levels. Yes, the three main bosses have their own unique difficulty levels. Any main boss remains open to fight again what your character already faced. "Master" difficulty demands 1 golden key. The next difficulty demands 3. The last demands 5 keys. As you only need to defeat one of the main bosses on its highest difficulty for achievement, for this purpuse I suggest the Cook, which is the easiest: least summoned creatures, slow, stays on the path, limited melee attack.
NOTE: these seem to be a on-etime thing. You can't re-play already won battles of these. And take caution, these DO get harder.
- defeat the three main bosses on Rogulike w/o using fountains: this is actualy entirely possible, as you can return to town for healing any time (in roguelike costs money), can use potions (recharge them in town, costs money - might be better option than healing?), and even find regenerating equipment around (does it slowly, so prepare for a lot of oldschool standing around)
- resurrect 8 time in roguelike: this obviously conflicts with the above mentioned award, and I assume it'll cost a ton of coins
- Game of Crows: this is unlocked in the hub-town clicking on the crows. By patches the crows differ in position, but not in order (so don't mind if a crow got in the background or the front). [url=LINK]https://www.youtube.com/watch?v=fR8zxx_2JrA[/url]
- The Alchemist: equip all 5 potion-cards on one character
- Captain Planet: equip all 5 ring-cards on one character
- Eeny, Meeny, Miny, Moe: this is actualy not that impossible, as the autohit function does not count. The auto-loot function though might get in the way. So what you need to try this is these prerequesit:
1) have 1-2 zombie on the map, preferable further from other monsters, but this is motly irrelevant, as you can try to be patient with letting the autohit get any other monster that gets in your way. ANY zombie-type works, like liches, or zombie-cows (aka. any monster that leaves behind a poison cloud effect).
2) a "crap" loot after defeating a monster, or bashing open a barrel/jar.
3) 5 barrel/jar.
So find your crap (literaly looks like a dung, worth 1 gold), and your zombie. Bash barrels, click on zombie once. Bash the other barrels. Click on zombie. Loot the crap (you don't click it, just swipe your mouse-cursor over it).
And that's how it works.

Rogue difficulty:

So, throw your strategy out of the window, because Rogue Mode (NOT difficulty) has a couple of rules changed:
- as mentioned, healing and respawning costs coins now
- you get way less coins (like one 5th, I think)
- because of the further lessened resources, say goodbye to identifying cards. That's just not an option anymore
- sure, I bet you want to not die. I have bad news for you: the game easily throws at you unwinnnable situations. And I'm not talking about separated optional rooms, oh, no. I'm talking about gargoyles coming to life, in group, jumping on your head, dealing critical damage, on the single path you have to advance kind of situations!
- to make things worse, a ton of equipments are simply disabled, more precisly and noticably the HP-regenerating amulet for starter, which now only works if enemy is in your attack-radius.
- and fountains do not replenish.
- though this might be an interresting thing: I used up like 1 or 2 mana only (don't remember, should test), and the healer refilled my mana for free! That's cool, potentialy abuse-able.

On classes:
- Archer/Rogue shoots arrows. Sure, you can't equip all elements and attack hoping the right element will strike, but still manageable. And if you realy want to be a pro, there's a change set of equipment button, like in the Dibalos.
- Mage has very noticable less HP at start. Its basic attack is ranged, and has a target seeking mechanism. Which is good if you can shoot around a corner, but bad if you have to pick something from a crowd. A charging crowd. Also, its cards are more "interresting" than useful.
Still, the coat that has orbs to push back closing monsters seems good, and the teleport card ceems a mandatory escape-from-danger device.
I still suggest to make it an all-HP build. Well, make any character an all-HP build for Roguelike.

Oh, and for Roguelike, I very much suggest, at the first bookshelves at the beginning of the first level of the Tutorial Dungeon get the Healing Potion. Anything else, and you are probably better off deleting the character and re-trying.

NOTE on Modes (Casual/Normal/Roguelike): you can freely switch between Normal and Casual, making them rather indistinguishable. Unfortunately I've found no way to switch to Roguelike from those two, so no easy training for you for that part.
Strange though, that I just noticed Roguelike is not encouraged either by a badge given for finishing the main story part with no deaths.

NOTE on the Mage:
While for a time he's very fragile, and his range is shorter than ranged enemy units, if you are lucky to find a couple of pieces of equipment, he can be a real powerhouse. These items are the Book of Ice and Fire (two item, I appreciate the reference), the cloak of orbs, teleport, medal of mana-regeneration.
It is true, that the medal only works when enemies are around, but you should use the teleport (and probably whatever else you find) scarcely, so it should be enough most of the time, sparing you coins.
The cloak pushes away enemies from melee range, and if you upgrade it, it'll have plenty of charges too.
The two books give elemental damage, and I'd swear powers you up generaly, making the character very strong.
The problem is obvious though: you need to find the items from a random pool.

NOTE ON CAULDERON:

It is pretty much useless.

First: you don't get the HP/MP boost (equal to your leveling - pretty much the reverse you spent manualy) at Roguelike mode. As you can just collect statboosts from shrines anyway spending another 100 hours playing, who cares for Casual/Normal where you pretty much never die anyway?

Second: as I've just collected the work of 41 clvl, I can safely say, no Legendary Card comes form the caulderon. Sure, magic cards can be better than the Legendary ones, but for a long time you won't care, for two reason:
1) achievement
2) legendary cards are bloody rare
Because of the later, I've counted on my caulderon to gimme a couple. But no. I'm deeply disappointed.

NOTE on maxed cards: the balance and possibility of combinations arise/changes a bit. That'sa good thing. Won't be a synergy-system, or proper deckbuilding, but still, that's at least something.

NOTE ON Fastest and Furiest:
Someone suggested to find a room with a spawner which makes 1 HP minions, lure it to the doorway, camp on the other side, and wait until it fills the room. Enter, and harvest.
The problem is with this, if I've counted properly, the maximum number of units in such roomo stopps accumlating (the AI disables the spawning ability) at ca. 120. That's ok for the Make Them Fear Archer Achievement (whatever its name is), and come to think of it, the Charge 'Em Warrior (whatever the name) achievement too, but the "kill 200 in 10 seconds" achievement must come from elsewhere, and I have no real idea where, aside maybe Master Quests, but those are dangerous (and I still have no idea how to replay them).

NOTE:
Legendary crads are totaly distinct thing from Magical cards

NOTE:
doing the massacre diff, no healing achievement is though. Not sure what this even means. Egthese factors count?
- death rage
- respawning
These factors seem to count:
- getting healed after respawn
- picking up hearts
- leveling up THIS IS VERY STUPID, PRACTICALYGUARANTEES YOU WON'T BE ABLE TO DO THIS UNLESS YOU MAXED THE CHARACTER'S LEVEL!
Advice: for this ach. you'll need 2 potions: invisibility, and divine potion (aka. invincibility). Avoid using invincibility unless you absolutely have to.

Ok, so the "pass a big dungeon on massacre difficulty without any source of healing"'achievement either does not work (wouldn't suprise me), or you aren't even allowed to refill mana (because of some bug I've started less than maximum mana).

Otherwise you are also not allowed these:
- drinking from a hp-fountain (obviously)
- picking up any health
- getting resurrected by rage
- leveling up (what means you have to be max. level to even try this achievement)
- very likely no regenerative items allowed either.

Note: you will NEED the immunity to electricity boots. Set one that does not drop you mana/hp (the legendary version does that).

Anohter note: if you restart the dungeon by X-ing it, the shape of the dungeon remains the same.