I did leave the origin of Xagthrath the Grumbling Rug and blgthrths in general rather vague.
Though I do have in the mind’s eye an image of an angry blgthrth sitting in a corner “agrily screeching and buzzing its towel like corners in a menacing fashion and the eyes, oh God why does this towel have slit like black as pitch eyes just above a similarly slit like mouth?!”
It blinks rapidly as it does a threat wobble accompanied by the buzzing, eyes sit in an angled “V” like angry eyebrows, and the mouth just opens and closes with the outraged screeches and squeaks.
That fits right in with the present narrative ...
https://www.youtube.com/watch?v=V6H01cUSpfQ
https://www.youtube.com/watch?v=A76g-tHt4A0
Blgthrth motion.
Imagine it slightly less severe, but wriggling through the air.
While screeching angrily.