Salem is a medium-sized black cat that the party found in the archives of the Arcanium. Although his powers seem to be limited outside the fey realm, there is definitely more to Salem than he lets on. He developed a strong affinity for Mork, and has learned to communicate with his half-orc owner/servant in Abyssal.

Salem is a (possibly demonic) black cat found by the party in the fey realm beneath the Arcanium . He claimed to to have been stuck in the archive for several hundred years, once his former master had passed. He made a deal with the party: he would help them defeat the gauth guarding the archive, and they would release him from the room where he was imprisoned.
 
Upon crossing into this plane of existence he seems to be a normal black cat, no longer able to speak common. However, he has taken a liking to Mork and can speak to him in Abyssal. He also seems to have the ability to teleport short distances, and possibly plant suggestions in peoples' minds.
 
After saving the party from losing a fiddle playing contest on the Island of the Lost, Salem was able to temporarily teleport back to his home dimension. For reasons unexplained, he can now channel his inner best and turn into a ferocious Hellcat when sufficiently provoked.
 
Salem seems at home in Monterra, and quickly establishes a cult that worships him as the embodiment of the Old Gods.  He begins referring to the Scions of Hersey as his "apwastles," and notably, uses his demonic powers and his large following to help defend Monterra from Trogdor's assault on the city.