Sardior

While Sardior is known to be worshipped by several Gem-Dragons, details of his worship are a well-protected secret. So, not much is known about this elusive deity, only that he's related to Bahamut and Tiamat (supposedly their first, shared creation) and that he's the supposed creator of Gem Dragons and Gem-Dragonborn. It is said that he perished when the first war between the deities of Sancstoryl was fought, but his conciousness supposedly lives on; enough to bestow powers to his followers.