Mindwitness

Mindwitnesses were flying nightmares of eyes and tentacles created by mind flayers by inserting one of their tadpoles into a beholder.

Description
A mindwitness greatly resembled its beholder "parent"; an orb-shaped being in diameter, with a large central eye on its body, and ten smaller eyes on stalks emerging from the top. However, a mindwitness's mind flayer influence made an already horrifying creature arguably even more so; its fanged mouth was replaced with one more akin to that of a lamprey, and this maw was surrounded by four large octopus-like tentacles.

A mindwitness's body was, like that of a beholder, naturally buoyant, allowing it to fly and granting it effects much like that of a feather fall spell. Its many eyes granted it 360 degree vision, preventing it from being flanked and making it generally very difficult to avoid being spotted by one. Mindwitnesses also had an innate resistance to spells and were able to project an antimagic field in a cone in front of them.

A mindwitness was able to communicate telepathically with any creature that had a language, and was itself able to speak both its own language and Common.

Combat
In combat, a mindwitness behaved, unsurprisingly, much like a combination of mind flayer and beholder; using both the flight and eye rays of a beholder, and the illithid's fearsome psionic and brain extraction abilities.

A mindwitness would typically begin by unleashing a mind blast on its opponent, then follow up with eye rays from its ten stalked eyes. Like a normal beholder, each eye had a different power, namely: charm monster, charm person, disintegrate, fear, finger of death, flesh to stone, inflict moderate wounds, sleep, slow, and telekinesis. In addition to the abilities granted it by its eyes, a mindwitness was also able to use the following psionic spells: charm monster, detect thoughts, levitate, and suggestion. If forced into melee combat, a mindwitness was able to resort to attacking physically with its tentacles.

After stunning or otherwise befuddling its target, a mindwitness would then attempt to attach all its tentacles to its opponent's head so as to extract its brain, instantly killing it (barring creatures with multiple heads, such as ettins and hydras).

Society
The main purpose of mindwitnesses within illithid colonies was to improve and accelerate telepathic communication, since mindwitnesses were capable of maintaining a telepathic link with up to seven other creatures simultaneously. As part of the ceremorphosis process, mindwitnesses were imprinted with absolute devotion and submission to commands, so if separated from its mind flayer masters, a mindwitness would seek out other creatures to serve. They were known to ally with flumphs and other telepathic beings such as demons.

Normally dwelling underground, mindwitnesses could be encountered as solitary creatures, in pairs, or in groups as large as six.

History
Qrr'zarq, a mind flayer who worked in the Xanathar's Thieves' Guild in the late 15 century DR, had plans to turn the Xanathar into a mindwitness.