Not much else in the module pertaining to Siragle, other than the following:
"Perhaps in battle, Siragle attempts to grab a PC and plane shift home, forcing the other adventurers to undertake a rescue mission to the fiend's gruesome Abyssal realm."
"This dangerous Abyssal denizen has been growing in power and influence over the past few centuries. He now holds sway over the 493rd layer of the Abyss, a small, loathsome place with few inhabitants or resources. Thus, the contract he drew up with Draskilion is of considerable importance to him, and he has decided to deal with the matter personally."
"Siragle's agreement is for Draskilion's soul and services. When he discovers that other beings have also been promised the wizard's soul, he will not be pleased. However, as he has learned to be flexible, Siragle will be happy to claim the souls of two or three less-willing persons, "who should have kept their noses out of this business anyway."