There are words that describe elevating a person into the divine: apotheosis, divinization, and deification as nouns, and deify as a verb. In some religions, it is possible for a human to undergo apotheosis (like Heracles in ancient Greek mythology); in Catholicism, the terms deification and divinization (but not apotheosis) denote believers acquiring salvation through becoming one with God.
Is there a single word that denotes the reverse, namely a noun for making a god into a demi-god, saint, or otherwise non-god entity? For example, pre-exile Israel had widespread polytheism, and books in the Hebrew Bible and Old Testament refer to the worship of multiple gods. 2 Kings 23:14 refers to removing items of worship for Asherah, a goddess who may have at one time been considered a wife to Yahweh (Wikipedia). In that case, human (non)believers choose to remove recognition of divine status. Alternatively, there are fictional mythologies where gods are cast down within the mythology, as may have happened with Aroden in the Golarion (Pathfinder) mythos. My target word would ideally refer to either situation:
Asherah underwent _____________ by the time of the Babylonian captivity. She was no longer recognized as a goddess within Judaism.
Many clerics speculate about the cause of Aroden's _____________ and eventual death.
I can think of one option. The OED attests undeify, but undeification is unattested in dictionaries I consulted and very rare (about 100 results on Google), so I'd prefer something more common if possible.