Xoblob's appearance is similar to that of an average beholder with a few acute differences. His skin is smoother, and he only has six eye tendrils instead of the usual ten--the others being transformed into illithid-like tentacles. All of his pupils are white instead of colored, similar to a blind man's eyes.
Xoblob is aloof and chaotic, with manipulative and deceptive tendencies. He is comfortable in inhabiting other creatures and using them as puppets to his fun; stretching the truth, omitting details, and pretending to be of lower intelligence in order to play games with those around him.
His favorite color has proven to be purple, as evident by his preference for the color in the Old Xoblob Shop along with the color scheme of his internal mindscape.
It is unclear when or how Xoblob was created, however he's mentioned that a deep gnome in the Undermountain was affected by Gas Spores and came back to Waterdeep carrying the parasite and believing himself to be Xoblob.
The Old Xoblob Shop
Within Waterdeep, Xoblob spent a lot of time in his deep gnome victim running the Old Xoblob Shop within the Dock Ward. This shop harbored many small purple trinkets and oddities--likely stolen from the trashcans of Waterdeep. This shop also harbored Xoblob Jr., who held an unusual favoritism with the mindwitness. It is inclear when and how Xoblob came to found the plushie dragon, aside from a mention that he found him in the Underdark.
When the Lif of the Party made their way into the Vault of Dragons, Xoblob somehow managed to follow along. In his deep gnome host, the parasite was weak and largely ignored by the party. However, this all changed when Anton and Levi went to negotiate with the dragon, Aurinax; where Xoblob managed to follow along. Here, Xoblob revealed his true form and attempted to take over the Adult Gold Dragon. However, his plans would be foiled by the tag team efforts of Anton and Levi along with some otherworldly help by an infernal third party. His plans foiled, Xoblob was then skewered and killed by Aurinax.