- In all environments of Chapter 2 ( Caves, Catacombs, Flooded Caves).
- Only in Catacombs and the Flooded Caves.
The Frail in its first phase has 100 HP like Pin and behaves identically with the only difference that The Frail is less accurate in its jumps and generally overshoots or undershoots Isaac.
Upon its HP being depleted, The Frail's appearance becomes skeletal. It now has 200 HP and performs the following attacks:
- Jumps out of the ground towards Isaac, firing 4 diagonal projectiles from the last section of its body that each split into 4 more projectiles in either cardinal or diagonal directions.
- Whether it fires projectiles depends on the length of its jump: does not fire projectiles on short jumps, fires projectiles shortly upon exiting the jump on regular/medium jumps, and fires projectiles both shortly upon exiting and after a few moments airborne on long jumps.
- Partially emerges head-first and:
- Partially emerges tail-first and fires a burst of white projectiles in all directions which leave small puddles of slowing White Creep where they land.
- After performing this attack, The Frail will always jump or appear head-first out of the same spot it entered.
Champion Versions 
- Black: Starts in its second phase, with only 66.6% HP (200) total.
The Frail as one of Delirium's forms.
- It is the posthumous version of Pin.
- Despite The Frail being an invertebrate, or an animal lacking a skeleton of bones, its second phase is skeletal.
- The definition of the word frail is weak and delicate, which explains its rotting body and depressed look in The Frail's first phase.
- The main body of The Frail's battle sprite is heavily based on Larry Jr.'s battle sprite.
- The Black Champion's behavior of starting from the second phase might be a bug since this version of the boss is set to have 30% more HP (260) in its first phase. Spawning the black champion via the Debug Console displays a glimpse of the boss in its first phase, before being instantly replaced with the second phase, ignoring the amount of HP set in the game files.
- The Frail can be found in The Void, even before being unlocked.
- It is the boss version of the Pasties.
|Bug!||If The Frail is under the effects of Broken Modem in mid-air, its jump will be stopped and it will fall.|
|The Binding of Isaac: Rebirth|
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