Arak'ar

The Arak'ar were presumably either one of the many broods of Anub'arak or a secluded group that fell under the Anub'ar brood. They were mostly scientists dealing with the preservation of the Nerubian race after its majority fell to the plague of undeath. Whilst their main goal was to reinforce the numbers of the Scourge, they were still largely loyal to the interests of Azjol-Nerub. With their perception twisted by the Lich King's corruption, many of their experiments were considered nightmarish even by the standards of the Cult.

The arak'ar parasite
The arak'ar parasite was developed sometime during the Scourge war. Most of the research behind it was destroyed, and as such it is impossible to replicate the original result. It served to infest the (mostly undead) humanoid races of Azeroth with Nerubian chitin; such allowed those forced into Nerubian service to better scale the Underkingdom. It also made them suitable hosts for other experiments. Those that would survive the procedure were called the arak'a.

While the parasite has no will or intelligence of its own, it has a constant need to feed. It will devour the host and then itself if not fed otherwise.

The Arak'ar attempted to create strains that would give the host additional limbs or even Nerubian crypt wings, but human minds proved unsuitable for controlling such. Either no connection was made at all or the host's mind became overwhelmed, resulting in final death.

Lyrric and Alarric the only known still living hosts.