A cult-like faction that sponsors gods and unsettles even hardened lawyers.
The Nebulars come up once, in passing, and the way they come up says everything. Quasar — a nullian attorney with no filter and no reverence for anything — calls them "those weirdo Nebulars" while explaining that the god Ysalte was sponsored by them, and that Ysalte's sponsorship is what made her death-mark on Louis such a serious problem.
That is the whole of the public record here: they sponsor deities, they are strange enough that professionals say so out loud, and their god was killed by a crawler who had been turned into a card.
Never seen; known only as a sponsoring body strange enough to be described as weirdos by someone with no standards.
The faction sponsoring the god Ysalte, and a strand of the crawl's religious politics running under the eighth floor's events.
Also appears in books you've already read — spoiler-safe to their endings: