"Trap their spirits to fight for you before they can flee the battlefield."Raise Ghost is a third-level Death Magic spell in Heroes of Might and Magic IV that costs five spell points and creates a stack of ghosts from any stack of living creatures with dead members.
Raise Ghost works in a manner identical to Summon Spells, except that Raise spells are restricted in that there must be a unit with creatures to raise. What this means is that you must target either a live stack with dead members, or a dead stack, and that you are limited in the number of creatures you can produce by the number and hit points of fallen creatures from that unit.
If, for example, you can raise twenty ghosts per casting, and you cast it on a unit of 30 magi that once had 40 members, then you will raise ten ghosts (the ten fallen mages will be raised as ghosts). If the other 30 magi are killed, then you can cast the spell on the unit again, and get twenty more ghosts, and even once more to get the last ten.
The Necromancy Ward spell will prevent you from raising any creatures at all for the rest of the battle - unless you start removing it from stacks you want to raise.
As with all Summoning spells, the ghosts thus created vanish when the battle ends.
The ghosts created by this spell are fast, and though they don't do much damage in combat, they have a devastating touch that ages the target. This effect reduces the target's attack by 25%, reduces defense by 20%, and slows the target's speed and movement by half to boot. This spell can therefore be thought of as producing a mobile ageing spell, and because of this effect, Raise Ghost can be very useful even in a huge battle. Though the ghosts may not survive their maiden voyage, they can deliver, by touch, one of the most vicious debuffs in the game - one that affects stacks of all sizes equally.