First one: In this version of Norse cosmology, where do non-warriors go when they die? In the normal version, they go to Hel, whether they've been good or not, but that seems rather grim and dark for UF.
Second: Where do Cephirans go when they die?
They don't go to heaven where the angels fly
They don't go to the lake of fire and fry
As far as I can tell, they just go bye-bye.
In more serious terms, no Cephiran has been spotted in the ranks of Valhalla or in the dishonored dead. If they had, then certainly someone would have found out about them. Are their souls elsewhere, or do they just vanish?
Third: Surtur threatened to burn the Nine Worlds in fire, as the prophecy stated, but what would have happened to Cephiro if the Ragnarok had gone off as planned? It's not one of the Nine Worlds mentioned.