Mercurius

Effects

• +0.4 speed.
• Opens most doors after entering a room, even in rooms with enemies, allowing Isaac to leave at any time.

Notes

• While (Door Stop) Door Stop has a similar effect, Mercurius has the added benefit of opening the doors that Isaac did not enter through.
• Does not open the (Boss Rush) Boss Rush door.
• Does not open any Special Rooms, including those that require pickups to unlock. Doors won't be opened even if they were open already (such as (Treasure Room) Treasure Rooms and (Shop) Shops on the first floor, (Sacrifice Room) Sacrifice Rooms, etc.) or have been entered before.
• Does not open doors to (Red Room) Red Rooms if those door are created while there are enemies inside the current room.

Synergies

• 4.5 Volt / Jumper Cables: Provides infinite charges by clearing some enemies then leaving the room, and repeating.
• Charm of the Vampire / Gimpy: Allows the possibility to generate unlimited Hearts.
• Head of the Keeper: With enough patience, Coins can be gathered infinitely.
• (Tainted Keeper) Tainted Keeper: Leaving and re-entering the room allows for limited coin farming; however, enemies in rooms Tainted Keeper has already visited will eventually stop dropping coins.