Established premise for Weird Uncle Ardyn AU: (so i can track shit because i am forgetful as heck, to be edited as needed if this becomes A Thing)
At some point Regis stumbled his way onto Angelgard and found Ardyn, instead of Verstael, and brought him back to Insomnia to recover there
Because of Ardyn's absence, Niflheim did not so easily create a magitek army, and they also had to deal with a non-subjugated Ifrit trashing the place whenever he woke up; both issues meant Niflheim was not so much of a threat and Lucis was a little safer
Over the years Ardyn has become something of a weird unchanging cryptid in the Citadel with ties to the royal family
no subject
(so i can track shit because i am forgetful as heck, to be edited as needed if this becomes A Thing)