eidolon

A dark wisp of smoke—Percy guessed it must be an eidolon—seeped into a Cyclops, made the monster hit himself in the face, then drifted off to possess another victim.

“Leo...that’s what happened to Leo. He was being controlled by an eidolon.”

Helen doesn’t ask anyone at Prime Space to explain her mission’s name, Eidolon, but if she’d checked Wikipedia, she would have learned that an eidolon is a phantom in human form.

Still it exists, and it is there that the astral eidolons of all the beings that have lived, animals included, await their second death.

There is no such thing as the god Apollo, and 227science makes a clean sweep of Apollo and Dionysos and all such fictitious objectivities; they are eidola, idols, phantasms, not objective realities.