I would just ask yourself this: Elbaph essentially worships Nika and knows enough about him to know what he sort of looked like right? Why do none of them know what Loki actually is then as well? They've guarded the fruit for hundreds of years. They have the Harley text in front of them, its been studied and not one of them actually specifies if Loki's fruit is a deity fruit like Luffy's.
Worse yet, Imu doesnt recognize Loki's power. Which tells me no one has used it in the last 900 years at least (i.e. why I dont think its the Forest or Sea Gods because Imu would presumably know about it).
Personally I think Imu is the Earth God and has an affiliation with a Hell Serpent, but thats just me, given they fought the Sun God.
But yeah we can agree to disagree on this and wait and see what gets stated.