What's up with Bahamut?

[Beddict]

Aside from Bahamut, Enkidu, Thordan, and the Bozjan queen whose name escapes me just now, we have no irrefutable evidence that any of the primals ever actually existed beyond folklore before being summoned.

Garuda is another one. The Ixal are a chimera race created by the Allagan Empire originally known as the iksalion, and designed as soldiers for the Garuda Airborne Division led by a female general. The iksalion were indoctrinated to unfailingly obey specific individuals, and it's presumed that their indoctrinated loyalty to the female general eventually became worship, their past fading into myth as the general became known as Garuda. Azys Lla also faded into myth after the fall of the Allagan Empire, and is now the Ixali promised land, Ayatlan. Source is the quest An Unwanted Truth and Encyclopedia Eorzea Vol. I Page 249.