The Master Wraith is the most powerful of the Wraiths in Mordavia. It is encountered at night in Quest for Glory IV: Shadows of Darkness, by traveling five screens south from the Cemetery. It is apparently the spirit of Gregor.
It is unknown how this undead spirit came into possession of the Heart Ritual, however, in the Monastery, in the readable book, it mentions that a person called Gregor has the Heart Ritual but that he has gone missing in the forest. The Paladin Piotyr fought the Wraith in his search for the Dark One Rituals, and was slain. The Master Wraith took Piotyr's Sword and added it his collection of treasure. Devon Aidendale defeated the Master Wraith many years later.
The rewards reaped from this battle depend on the hero's class, though it always includes money, jewelry and bones.
Special class loots:
The Magic User gets a spell scroll.