User blog comment:B214/Question and Answers 6/@comment-185.112.105.215-20170130111628/@comment-9595671-20170131024020

Regardless of strength, some Devils would probably want them over the current system, but considering these Devils are mostly those from the Old Satan faction that's in ruins...

Plus the only way they could do that is with Valerie's Sephiroth Graal, and their souls might already be gone so even she can't revive them.