Since the DDI Jubilex article is of interest here, a short summary about it. Like other articles it describes his history and lore, themes for his followers and minions, and a write-up for Darkness Given Hunger. It has nothing on the Alkilith in case anyone was wondering.
Jubilex is described of as being underestimated by everyone including other Abyssal Lords. It's said he's not even aware of Zuggtymoy taking over the surface of his realm. Dagon and Pazuzu wrongly suspect he was a fallen Obyrith Lord. He's not mindless as some sources have called him, but actually knows a lot about the nature of the Abyss and is consuming more and more knowledge. And instead of an Aspect he can possess an Ooze anywhere. His specific origin is that he's the residue left over and given sentience when the Abyss was created by the Seed of Evil from Tharizdun, when it started eating away a part of the Elemental Chaos, and apparently he knows the true names of all the Obyrith Lords and their nature as a result.
That sounds pretty interesting, though I'm not sure how an entity that's continually consuming knowledge from everything he touches, who knows the true names of all the obyrith lords, isn't aware that Zuggtmoy is trying to conquer his layer.