Merciless ones are aquatic parasitic aberrations[1] in all likelihood related to faceless ones. They are cycloptic, squid-like creatures with a body shape similar to Ozumat. They attach themselves to the heads of things to enslave them, and can affect their host's mind even when "dead." As the Beak of the Merciless One shows, they have beaks.
This article or section includes speculation, observations or opinions possibly supported by lore or by Blizzard officials. It should not be taken as representing official lore.
They may be a cousin species to the Faceless Ones, also an ancient aquatic like species who serve the Old Gods.
They may also be related to the kraken, Ozumat is called this, but given his ability to attach to victim's heads and control them, he is also thought to be a large variant of Merciless One.