Asmodeus Himself is literally the only being who could possibly have ordained that Keltham not be a pile of ash in this moment.
"Keltham, I'm sorry, but my time really is up now," Isidre says. "I do think I'd recommend going ahead with this course of action, over leaving things as they are, and I have no time to plan more. Talk to Carissa and let me know whether to move forward on meeting, and then confronting, the Queen."