If you make an absurd claim, the burden of proof is on you.
It's that simple.
... because if that's NOT true, then I just pulled Gilgamesh out of my anus, and he's standing right here, ready to smite anyone I please, 'cuz he's all up in your bidness like dat. And there's nothing you can say about it since it's up to YOU to prove that I didn't just pull Gilgamesh out of my ass.