Wraiths usually haunt a particular spot, thought to be their grave, because it contains some valuable goods (such as gold) they can't leave behind, and therefore, are confined to it. Wraiths were brigands or thieves during their lifetime, and their own greed fuels their very existence. Wraiths have the ability to drain the life out of any living creature (including the Hero) which does not have some form of magical protection, therefore defeating them without it is nearly impossible. The deadliest of them is the Master Wraith.
There are seven Wraiths in Quest for Glory IV. Five of them can be found in the Forest at night, one in the Castle, and another one in the Cemetery.
Wraiths usually leave behind the largest loot pile of all enemies, and defeating just some of them can provide enough kopeks to the Hero for the rest of the game.