Faction War prologue page 4
What are these creatures?
Doesn't sound like anything good, possibly chaotic. I thought it could be related to the theory that the Lady is a reformed tanar'ri lord.
Remember that the Faction War prologue takes place so long ago that even Shekelor thought of that era as ancient, and Shekelor lived ten thousand years ago. It was before the oldest known human empires, probably even before the illithids. The dominant races on the planes may have been elves, serpentfolk, giants, Sarrukh, Aeree, Juna, aboleths, or other races now forgotten.
That said, I kind of assumed that the gyoxchuggi were simply an older name for the dabus, who travel the Cage unrestrained by anyone, or perhaps the tanar'ri or baatezu. If the name is inspired by the name Gygax they might be a race of creators, perhaps the creators of the Ring of Gaxx artifact. The Sisters of Iron were surely an early faction devoted to suppressing heretical beliefs. They were probably similar to the Harmonium.
Gyoxchuggi as an early name for the dabus makes sense. Alternatively, maybe they were a race that preceded the dabus. There's a vague implication that the race wandered about Sigil and behaved however they wished (otherwise, why invoke their name to describe somebody who acted in a similar manner?). Combine that with the notion of them being a race of creators. Maybe not heretical, but a race of chaotic-leaning outsiders who would go about the city making changes according to their whims. That could then tie back in to why Sigil sometimes reorients its layout from time to time. It could be the work of some still-active (but extremely secretive) gyoxchuggi. Or maybe they somehow fused their essence into the city.
Sisters of Iron is probably as rip says: A faction devoted to suppressing heresy.
The third name in that paragraph is intriguing: The Bank of Keys. A place where keys to all known portals were collected and lent out?
Lovecraftian creatures usualy have ''gg'' in their names.
The Bank of Keys probably was too much trouble and got mazed.
Whoever they are, they sound like a profane and heretical bunch. Gyoxchuggi has a guttual sound to it, and usually those sorts of sound associations link back to races with a tendency towards evil. Goblins, bugbears and more fiendish races. So - wild speculation - they're probably a bunch of lower planars who enjoy preaching contrary/heretical beliefs about good aligned powers.