Level 3 of the Unofficial RPGGeek Community OSR Dungeon, with each level designed by a different user.
From the Introduction:
The majority of this level is an ancient magician’s academy, connected to the rest of the level by temporal and planar magic. The wizards and their students are long-gone, but many interesting relics and creatures still occupy this area. The Dark Temple materialised as part of the same magic that drew the Academy to this plane, perhaps as a balance against the generally good nature of the academy.
DocX version of the 3rd Level of Black Keep Castle, the unofficial RPGGeek OSR Dungeon.
Contents: One ancient school of wizardry, several humanoid tribes and a terrifying dark temple to an unhallowed god.