[Perdition]

Life Drain isn't based on blood, it's based on focus. Blood is just the vessel for the focus that's being drained. Unconscious and at 0 HP the person wouldn't have any usable focus. Even then, life drain should be a 1:1 conversion of damage to HP. You can't do damage to someone with 0 HP, yet you can drain the damage value of your life drain? It makes no sense any way you cut it. I say this as someone who uses life drain quite a lot, too.