Hello, i have been reading the creatures just for fun, and i think some of then should be reasigned or changed:
Undeads:
Weak spellcaster - Death acolite (or Plague acolite)
Weak spellcaster OR Strong spellcaster - Vampire
Weak builder - Undead gnome
Strong fighter - Zombie and Bone golem
Strong spellcaster - Necromancer
Guard - Ghost knight (why not some kind of legless wraith?) and Squeleton shooter
Special creature - Lich (i see it far more awesome than just necromancer, its a step above in undeath so why lower ranking?)
Villains:
Scout - Black raven
Constructs:
Scout - Change Giant eye into Floating or flying eye (kinda like the ones in fallout)
Guards and Strong fighter - Since they dont have mages you should give then lots of this:
- Strong fighter: Razor blade (high Power and speed, low hp and defense) and iron brawler (high def and hp, low speed )(Mech is too much sci-fi, steam punk like robot would be better)
- Guards: Shooter (magic muskeet like weapon, same stats as razor) and heavy gunner (granade launcher like weapon and flame launcher for melee, same stats as iron brawler)
-Strong spellcaster replacement - Hibrid (why not rename to Overmind?) the actual function plus researching
-Special creature - Terminator (a real match for the others elites, hibrid is far too pasive)
A good example on what style they shoud have:

Corpars:
Weak spellcaster - Mole-man chaman (c“mon a pegasus underground? no space to strech its wings, in any case should be a nigthmare, just make the chaman a fast runner or able to levitate )
Guard - Naga or medusa instead of griffin(which is a kind of pure melee creature), so Villains would have to do with only giants as strong builders.
As final notes:
-Pit demon needs a huge scary sword and serpent tongue sticking from its mouth
-Kreatur should be made insect-like, right now it looks like something made by a necromancer
- Is there a point in having Super creatures when you already got special ones?, i think its redundant, they should become summons instead, they would be too unbalancing along with specials, and summons would became more unique and cooler.
-Dragon seems so much more oriented to Villains than Corpars (money love and no morals) while Shadow Crawler kind of matchs the wild behavior of Corpars, so i would demote succubus to just caster and make dragon their special creature and Psychopath their summon, and put Shadow crawler as Corpar summon.
Well, i hope you read this and take some of my advices, creatures are either too few or random on some sides and much more developed on other, a bit of balancing and changing (for coolness shake) could be great.
Salutes.