So, there’s a YA book series called “Warriors,” which focuses on clans of cats. They believe in a clan of dead cats, called StarClan, who can tell prophecies. One character, Cloudtail, doesn’t believe StarClan, and can’t see them. It’s as if it’s only real to those who believe in it.
Would he be an atheist character?
Sounds similar. 
They would all be Atheist Characters. Atheists don’t believe in Gods. The Star Clan appear to be Ghosts or Dead Ancestors. That’s Ancestor Worship. the same shit that goes on throughout Asia. The dead, look after the living. If you take care of their dead bodies, good luck will come to you.
There are Asian countries where the bones are actually dug up, cleaned, worshiped, and then reburied after a few days. No gods required.
Fuck me, I try not to judge, but that can’t be hygienic. Please tell me they don’t make soup out of them before tipping them back into the grave…
Human beings is odd, end of story…
“It is believed that some South American indigenous cultures, such as the Mayoruna people, practiced endocannibalism in the past.[4] The Amahuaca Indians of Peru picked particles of bone out of the ashes of a cremation fire, ground them with corn, and drank as a kind of gruel.[5] For the Wari’ people in western Brazil, endocannibalism was an act of compassion where the roasted remains of fellow Wari’ were consumed in a mortuary setting;[6] ideally, the affines would consume the entire corpse, and rejecting the practice would be offensive to the direct family members.[6] Ya̧nomamö consumed the ground-up bones and ashes of cremated kinsmen in an act of mourning; this is still classified as endocannibalism, although, strictly speaking, “flesh” is not eaten.[7] Such practices were generally not believed to have been driven by need for protein or other food.[4]”
Whole lot of weird shit goes on in the world.