Quote Originally Posted by Singularity View Post
Tiamat doesn't want to be freed IIRC. She feels so ashamed of her part in the summoning of Bahamut that she believes she deserves her fate.

Otherwise I'm sure we could get her out without much trouble at all.
Yes, because of her part in the Primal Bahamut's original creation, she is chained there of her own free will. A form of self exile.