Which level 4 monster is the best?

It seems like you have three because of (probably) the Fortress.

Could you describe those creatures for me? (I mean their abilities, or whatever they're called, their special skills).
I know about the Ghoul, Nomad, Thief, and Fire Elemental.

Hmm... I don't remember the Fortress affecting the growth rate:confused: Without it, you can't build anything worthwhile, that's true, but the growth rate... you're exaggerating even a little bit. Okay, here are the ability descriptions, as much as I can remember:
Werewolves - Berserk, Lycanthropy (I don't remember the chance), and *2 chance for both when there's a full moon (days 14-16), Sorceresses - cast spells at a distance + chance to create a clone before attacking, Fire Elementals - fire wall after attacking (I also don't remember the chance), fire shield + fire immunity, attack with breath, Nightmares - breath, enhanced deadly gaze, fear, fearless. Sorry if I missed anything. If you have more questions, feel free to ask, I'll help as much as I can.