Rot Reaver

Rot reavers had the ability to create undead thralls using their parasitic reaver leeches. While these undead thralls were not nearly as strong or quick as ones made by unbonded reaver leeches, they were great distractions, and could be used to aid the rot reaver in combat. The rot reaver also had the ability to recover the reaver leeches from their thralls, which healed the rot reaver itself.

Rot reavers were made usually made in Whisper Tide Abbey from prisoners with horrific rituals that destroyed all previous traces of that person. They were also implanted with core stone shards which allowed the Order to be able to see and hear what the rot reaver heard, as well as allowing the rot reaver to also control the reaver leechs inside their body.

Rot reavers were clever and cunning and often followed their prey from a distance, sometimes for weeks, waiting for the perfect time to strike.   Rot reavers, while unable to speak, could understand sentances and even evesdrop on conversations.

Rot reavers had strong eyesight and hearing and could even somewhat see in the dark. They could also smell decay and undead tissue by tasting the air with it's elongated tongue. Due to the pungent and vile smell of decay, rot reavers were often able to track undead from miles away.

Rot reavers had a reaver leech living instead of each of it's arms, which it was able to control and use in combat as a whip or a piercing weapon. The reaver leach in turn was able to provide extra strength to the rot reaver, as well as help it heal rapidly.

3e: Rot reavers were initially created by the Order of Balance to hunt down undead and necromancers alike after the Terror of Hytheron. Reports indicated that the sucess rate of rot reavers was quite high.
  The Order took careful precautions with rot reavers and their existance, even nearly all memebers of the Order itself had no idea of them. They were usually unknown among the common people, and even those few who witnessed a rot reaver and lived to tell the tale, wouldn't have known what they were.   Despire being originally designed for tracking and hunting undead and necromancers, there were instances of rot reavers being used for other combat encounters and assasinations.   During the Long Dark, rot reavers had their control severed, and many turned on their former masters before fleeing into the dark wilderness.   4e: Many rot reavers survived the fall of the Order. Despite being freed from the control of the Order, many continued to hunt undead and necromancers due to not having much indipendent thought. A few did manage to band together and hunt together.   Some rumors claim there was a rot reaver mercenary, though there isn't enough evidence to prove this...