Under the Paleogean Serpentine Mound

d12
1. Giant mummified serpent demigod: remains inert until the stars are right
2. Emptied of original contents centuries ago, currently occupied by a witch's workshop dedicated to creating intriguing new life forms using recycled parts
3. Somewhere within the entirely earthen mass a single enchanted gem links the site to a particularly snaky dimension: luminous spirit snakes in their thousands writhe about the environs nightly
4. Entire membership of ancient vampire cult entombed within in quasi-dead  condition, seals regularly re-sanctified by snake god-worshipping zealots in nearby enclave
5. Imprisoned spirits whose magically preserved bodies must be destroyed before they can rest
6. Spectacular weregild offered by an extinct people to appease the gods of the serpent men, undisturbed for 1000 years
7. Time capsule of the ancient ones: strange and incomprehensible arts, magics, and technologies stored here until scheduled opening in 499 more years, giant auto-snake throws flames, launches explosive projectiles, bombards with deadly radiance any who dare break the seal
8. Fancy mausoleum for royal houses of the serpent men: every trap sprung, thoroughly looted, now a breeding ground for slimes, oozes and jellies
9. City of the mound devils: tiny entities of unquenchable malice and irony decorate the interior with furnishings crafted exclusively from human bones
10. The ancient earthwork merely serves as a corner in a continent-spanning pentangle that will one day call down the Missing Gods from their long sojourn among the stars
11. High priestess of the serpent folk abides in stasis with several drones, mated pairs of now-extinct antediluvian species awaiting the next Swamp Age
12. Snake-shaped air/sea/spacecraft covered in naturally accumulated turf