This is basically the premise of the BIONICLE serial "The Powers That Be". Kopaka and Pohatu are trying to figure out who's been murdering some of the most powerful beings in the universe, Including the local Lovecraft-Shout Out, Tren Krom.
Though it's subverted in the case of Carapar, who tries to kill the Lovecraft Shout OutTren Krom and gets disintegrated by the thing's Eye Beam for his efforts.
The basic premise of the entire story, is it's Big Bad, Makuta Teridax pulling one of these on Mata Nui, the Bionicle god, by poisoning him and casting him into a deep sleep, allowing him to rule over the Matoran people.
In the film Mask Of Light, Takanuva, the Toa of Light fights Teridax (who is basically Satan) and wins by pulling off his mask and dragging him into a pool of protodermis, fusing the two of them together. They emerge fused together as a single being named Takutanuva with Takanuva in control due to Teridax being weakened by the loss of his mask. They get seperated when they're flattened by a giant door. Long story. Anyway, Takanuva is resurrected but Teridax survives as a spirit.
Later he gains the powers of a God and becomes ruler of the Matoran Universe, later having a showdown with the Matoran god whose power he stole, Mata Nui. Despite now being the less powerful of the two, Mata Nui defeats Teridax by pushing him into the path of a speeding asteroid.
