Some skill questions:

1: Can the Hardened skill ability raise damage, so if you would set the minimum damage taken to like 15 and have a unit that does 3+1D2, would that unit get increased damage against it.
2: Are there some hardened skin abilities that stack with each oter.
3: Do Critical Strike, Bash and Drunken Brawler (Don't know if thats the one, but the C. Strike/Evasion mix) and Evasion stack with each other, or are they based of the same skill?
4: Can you have Critical Strike, and gain Bash trough an Item, can this be made with any item skills?

I can answer a couple of those with authority. The *damage* part of Critical strike, Drunken Brawler and Bash all stack with each other and themselves, NO evasion skills stack.

Critical Strike, Drunken Brawler and Evasion all count as different base skills - so if a unit has all 3, all 3 icons will show.

Note that you can give a unit multiple critical strikes, only *1* critical strike icon will show, but the unit will benefit from all the critical strike skills. Say a unit has two 20% 2x damage crit strike skills, it has *2* seperate chances of dealing 2x damage. For a unit which deals 40 damage one of 3 outcomes would be possible on every attack:
1) No critical strikes.
2) 1 Critical strike for 80 damage.
3) 2 Critical strikes for 80 damage each, 160 total, this will show as two overlapping 80's, not one 160.

There isn't really a limit to the number of critical strikes/ bash skills you can give a unit... I've put about 200 on a unit and every one was boosting damage.

I have another question about skills, I have read somewhere about that Bash damage ignores armor, is that true?

as far as i know, yes, its "spell" damage, not normal damage

Wasn't sure, since they implemented physical skills in TFT...

-Thought of another question, where do you find the Lightning projectile art, used for Chain Lightning, Forked Lightning and so on, the usual missile art doesn't seem to work, its just a small lightning-coloured sphere. Perhaps I have just gotten the wrong Missile art, or do you have to import it or use a custom path?

Yeah giving units or spells that effect is tricky. If it's a unit missile you want it for then you need to use the chimaera passive invisible ability called "Lightning attack" fiddle with it and you'll understand it's function. However if you want to give the lightning bolts to say an ability that's even trickier...You'll need to use .txts from the mpq and so forth but I'm not even sure if that'll work since very few abilities have the code to allow you to add in bolt/chain type artworks.. Anyway, best of luck to you

the bolt (finger of death\pain, chain lightning, forked lightning, chimera attack) art are hardcoded into the .mpq, i have no idea how to change them, add them, or if its even possible.

but how can a unit have the "Forked lightning" as a missile ?
that thunder is pretty cool, and imagine archmage blasting those ghouls with that one ......