The OSR is Dead (again, and again)
The Toad Priestesses feed the creature they keep in the vault on a porridge of moon groats and their own blood. The creature tells them secrets of the past, the future, and the forms of magic itself. Eventually the creature ceases its gibbering pronouncements and falls into a catatonic state. The Toad Priestesses butcher the creature and harvest its glands and offal to be dried and powdered for later use.
A human youth is fed the brains of the dead creature and shackled in the vault. Their hair and skin sloughing off as tentacles and additional mouths split from their flesh. Eyes and ears that perceive things beyond the here and now sprout here and there in unpredictable ways. This new prophet is tended to as the old one was, by the Augurs and the High Priestess. Only she knows whether this new creature is a distinct being, or one of infinite lives of an eternal thing, or perhaps a worldly avatar of some consciousness from beyond the stars.
Occasionally magi from the world will evoke rituals that whisk them along the aetheric winds to the Moon of Patala, that they may consult the Priestesses. Such magi keep careful watch on their apprentices (if they bring them). Some less scrupulous bring captive youths to exchange with the Toads for their knowledge, while others bring earthly foodstuffs or wares. Amongst the wise it is known to Beware the Toads of Patala.
This post was inspired by a bluesky post which can be found here. Beware the Toads of Patala is the title I received for the Appendix N Jam hosted by Lex Mandrake and jorphdan.