Dunwich Horror track
From Arkham Horror Wiki
The Dunwich Horror Track is a board element of the Dunwich expansion board.
Whenever a monster enters a vortex on the Dunwich board, a Dunwich Horror token is added to the track and the terror level increased by 1. Certain encounters can also result in either the placement or removal of tokens from the track. When the track is full, the Dunwich Horror monster marker is placed on Sentinel Hill. If the Dunwich Horror is defeated in combat, all tokens on the track and the monster marker are removed from the board.