|Speed up + you feel elusive|
Mercurius is a passive item.
- Doors stay open after entering a room, even in rooms with enemies, allowing Isaac to leave any time.
- Increases speed.
- Isaac can enter Mini-Boss Rooms and Boss Rooms freely but cannot leave without finishing a fight.
- Locked doors, boarded doors, and Arcades still need keys, bombs, or coins to be opened. Challenge Rooms and Boss Challenge Rooms cannot be entered without meeting the health requirements.
- Isaac cannot exit Challenge Rooms and Boss Challenge Rooms without finishing the fight.
- This item's name, its effects and the player's appearance when picked up are references to the Roman God Mercury (known in Latin as Mercurius). Just like Hermes, his equivalent in Greek mythology, Mercury was said to possess a pair of winged sandals which allowed him to move at unimagined speeds.