Sacrifice

[DGDobrev]

The problem is, that you do need to get a full HP unit (if the unit has 780 HP, you need to sacrifice for that much), even if the unit in question has sustained some damage. I suppose high int and lvl 3 chaos magic may cut it, but until you get to that point, it will be much easier just to buy that unit

[GodClone]

Use pacify before sacrificing a unit, increases its hitpoints by 50% , and its less to resurect after you dispell it or runs out . Having sacrifice,resurect and pacify at lvl 3 spells helps even more .