Alright here is the low down.
Zlandicar's heart gives what 12hp tick? As an iksar, I get 18hp tick for a total of 30hp tick regen if I have this equipped.
Arch Lich takes 31 HP/tick and turns it into 20 Mana/tick. Medding, I now gain 20 mana tick and lose 1 HP/tick.
Demi Lich takes 48 HP/tick and turns it into 31 Mana/tick. Medding, I gain 31 mana and lose 18 HP/tick.
As you can see. This iksar necromancer will never be /gsaying OOM, and your cleric won't have to be wasting heals on me. In fact, your necromancer can now become the healer for the casters in the group, and let the cleric deal with the tanks. I don't own this one yet, but I have put my natural regen to good use in groups by backup healing on casters so the clerics don't have to waste the mana. I can only dream of what I could do holding a dragon heart in my hand.
I would rather be a stupid iksar necro, than a dead softskin necro.

