Life Drain / Drain Life: Works on Undead &...?

[Graeme Dice]

tinkthank said:
1. Is Life Drain / Drain Life functionally identical but with two different names? Or are they somehow different, and if so, how?

One is a spell, the other is a weapon property.

3. I thought Undead were lifeless. Maybe not. In any case, however question #2 is answered: Will Life Drain work on those flagged "Lifeless"?

Only lifeless undead are lifeless. Life draining attacks will still cause full damage to these, but will not cause and fatigue or health gain.

4. Some items (such as the Wraith Sword) cast "Drain Life" automatically when you hit with a melee weapon. Others allow you to cast the spell "Drain Life" (or Life Drain?), such as the Standard of the Damned. Is there a big difference here in the way the spells work?

This is not what happens. The wraith sword causes normal damage to an opponent. The amount that gets through the armour is doubled for fatigue reduction, and halved for health gain.