Quote Originally Posted by Vlakorados View Post
Vitality reduces physical damage taken
Spirit reduces magic damage taken
Dex is your speed

No idea if they do anything else :)
You're almost right... Vitality and Spirit do the above on paper, but absolutely nothing in practice. Seriously, I've never known any enemy to do different damage to anyone at any level at all. Things that do 100 damage when you first meet them at level 10 will still do 100 damage when you're level 99, as opposed to, say, 1 damage, which you'd expect. The defensive stats in the game only seem to work if you augment them with a Hero Drink.