Stop Watch

Effects

(Removed in Afterbirth) Automatically inflicts slow to all enemies in every room, which slows them down to approximately 51.3% of their original movement and attacking speeds.
(Added in Afterbirth / Removed in Repentance) Inflicts slow to all enemies in the current room after the player is hit.
(Added in Repentance) Slows all enemies to 80% of their original movement speed and attacking speeds. This is separate from the slow status, and fully stacks with it.
+0.3 speed.

(Removed in Afterbirth / Re-added in Repentance) Once activated, the effect lasts permanently.
(Removed in Repentance) The background music is slowed down to 70% of the original speed of the music during the item's effect.
- (Added in Repentance) The background music is slowed down to about 90% of the original speed, not affecting boss tracks. The slowdown makes the music approximately 2 semitones lower.
The Broken Watch is an item similar to this item, but functions in a different way.
(Removed in Repentance)Because of the slow effect, champion versions of enemies will be tinted the same color as all other enemies. This makes it much harder to distinguish certain champion types, such as those that explode upon death.
Pokies, Slides and Mega Troll Bombs are not affected and will move in their regular speed.
(Removed in Afterbirth) Stop Watch is a special item.

(Added in Afterbirth / Removed in Repentance) Holy Mantle: Blocking damage with Holy Mantle triggers the Stop Watch effect.
(Added in Repentance) All Slow effects: Stacks with the status resulting in enemies moving at about 41% of their original speed.

(Removed in Afterbirth) Broken Watch: Overridden by Stop Watch; the speed up effect will not occur.
- (Added in Afterbirth) Both the slow effect and the rarer speed up can trigger at the start of a room.
  - (Removed in Repentance) This results in enemies being slowed to around 71.8% of their original speed.
  - (Added in Repentance) This results in enemies being sped up by 12%.