Random Gravity Trap

The walls are covered with floor-to-ceiling bookcases. On the ceiling, metal spikes hang down like icicles.

Gravity is reversed in this room. An unsecured creature or object that enters the room triggers a Failure. (Note: If this room contains creatures, they stand on the ceiling.) This room is identical in appearance to the Reverse Gravity Trap except that it has an upside-down door on the wall adjoining the ceiling.

Exploration. A Perception check or an examination of the bookshelves reveals that the books are shelved upside down against the tops of their shelves. The ceiling is 30 feet high. The bookshelves look easy to climb.

Books. As an action, a creature can make an Arcana or Investigation check to scan the bookshelves. On a success, the creature notices a spellbook (containing levitate or another 2nd-level spell) on a shelf across the room.

Roll initiative. Each round on initiative count 20, gravity reverses direction. Each unsecured creature and object in the room when gravity changes falls up or down, as appropriate. Creatures take falling damage and spike damage when falling up, and falling damage only when falling down. A creature holding onto the bookshelves when gravity reverses must make a Dexterity saving throw or lose its grip.

Once a creature has noticed the location of the spellbook, the next two successful Arcana or Investigation checks reveal the locations of other valuable books, each containing a spell, information, or a Minor Treasure.

Spell Effect. This is a transmutation effect created by a 7th-level spell. A successful dispel magic disables the trap.