The Father of Disigil, Now Deceased
See Monster Manual II for arcanaloth stats.
Krell conceived the project that eventually became Disigil, and convinced the Lords of the Nine to build it. He was murdered by its master, Alocer, who believed that Krell planned to seize the Iron Cage for himself.
Image by Tony DiTerlizzi, from “A Player’s Guide to Conflict” in the Planes of Conflict box set.