User blog comment:B214/Question and Answers 4/@comment-202.152.202.220-20141012094303/@comment-24421137-20141012204828

....How? We haven't seen her personality or anything, forming a peerage involves a lot more then just power.

And to answer your question yes Tiamat can be recruited by in a peerage, since Tannin was reincarnated by Mephisto, and he was a dragon king.