Hairpin

Effects

Fully recharges Isaac's active item upon entering a boss fight.
- This effect only occurs the first time a Boss Room is entered; leaving and re-entering the Boss Room will not result in more recharges.

The trinket's effect will trigger once for each and every Boss Room. Even if there are multiple Boss rooms on the same floor for whatever reason ((Curse of the Labyrinth.png) Curse of the Labyrinth, (The Void) The Void)
In Greed Mode, grants a full charge only for the two boss fights on the final level.
The effect is identical to picking up a battery, with caveats listed in interactions.
(Added in Repentance) Recharges twice on (Corpse) Corpse II: 1st time happens when entering the boss room, 2nd time happens when entering the (Mother) Mother fight.
(Added in Repentance) Does not fully recharge between (Dogma) Dogma and (The Beast) The Beast.

(The Battery) The Battery: If the item doesn't have a full first charge level, it will be filled. If the first level is full, the second charge level will be filled.
- (Added in Repentance) The item will gain both its charges.
(Mega Blast) Mega Blast: Mega Blast gains only 3 charge units.