Operator:
- Master (Attempted)
- Sisterhood of Jhe (Attempted)
- First Evil
Location:
- Sunnydale (Formally)
- Cleveland
- Easter Island
Miscellaneous:
- Created when a Deeper Well was used to cut a path to another dimension
- Hot spot for supernatural activity
- Sent out mystical energy that affected the nearby population
- Attracted supernatural creatures even when closed
- Distortions of the laws of physics were made possible by the Hellmouth's influence
- Opening a Hellmouth posed apocalyptic threats