Level 12 DiseaseBrain Fluke

This minuscule, wormlike parasite concludes its adult life in a victim’s brain.

Stage 0: The target recovers from the disease.
Stage 1: Initial Effect: The brain fluke bores into the target’s brain. The target gains vulnerable 5 psychic and has a -2 penalty to Will defense until cured.
Stage 2: When the target is under a charm or fear effect that allows a saving throw, the target must instead succeed on two saving throws.
Stage 3: Final State: The target is dominated by the brain fluke. The target spends most of its time eating to nourish the parasite before its spawn bursts from the brain two weeks later, killing the host.
Check: At the end of each extended rest, the target makes an Endurance check if it is at stage 1 or 2.
21 or lower: The stage of the disease increases by one.
22-26: No Change
27 or higher: The stage of the disease decreases by one.

Published in Forgotten Realms Campaign Guide, page(s) 103.