ToME: the Tales of Maj'Eyal

I have no idea what it does. Armour raises it, but it doesn't decrease my stamina.

Fatigue increases the amount of stamina/mana/.. consumed by talents.
It does not seem much but it makes you go dry much faster

Ahhh, that is actually rather cool.

Though, I also don't know what the difference is between Armor and Defense...

Near as I can tell, armor reduces (physical only, possibly) damage taken while defense reduces the chance of being struck at all.

Providing you can deal with the fatigue hit that usually comes from the first, it's generally a much better investment than defense is; even a character with a high defense is still going to get smacked occasionally, while a high enough armor score can reduce damage to single digits -- or even entirely mitigate it. 'Course, defense can dodge certain elemental attacks that armor wouldn't do much again, so there's a trade off in there.

Lastly, armor is technically finite for most classes, while defense (having a stat component) is theoretically unlimited, so given enough time defense could end up the higher number. I don't think we'd see that in the game as-is, though.

armor actually also reduces all non-spell attacks (except for ego weapons extra damage).

defense is not really unlimited because stats are capped at 60 (base, items can increase beyond this).

but yeah other than that you are correctish frumple