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Circle of Protection is a passive item added in Afterbirth.
- Surrounds Isaac with a large white halo around him that pulsates.
- With each pulse, the halo deals contact damage to enemies equal to Isaac's damage.
- Each pulse converts any enemy shots touching the ring into friendly purple homing tears that have Isaac's damage and no other tear modifiers.
- Circle of Protection is based on a cycle of Magic: the Gathering cards of the same name, which similarly provide defensive effects to their wielder.
- Circle of Protection's in-game icon may be based on the band A Perfect Circle's logo. The pickup quote is also similar to the lyrics of their song Pet.
- Circle of Protection is also the name of a spell with a similar appearance in The Elder Scrolls V: Skyrim.