Pin

For the item with a similar name, see Safety Pin. For the trinket with a similar name, see Push Pin.

Pin is one of the bosses that can appear in Error: The given stage ("The Cellar") does not exist.. It is among the most common to fight, particularly because it can appear on later floors as an enemy.

Behavior

Sometimes, a Spitty, Conjoined Spitty, or Round Worm can accompany Pin at the start of the battle.

Pin will jump out of the ground attempting to ram the player, then burrow back in.
Sometimes it can fire four projectiles diagonally from the last section of its body when jumping out of the ground or/and when burrowing back into the ground.
Occasionally sticks its head out of the ground to fire an explosive projectile. After doing this attack, Pin will always jump out of the same spot it was when firing, making it easy to predict.

Tips

Each segment of Pin can be individually damaged, so a single piercing tear could hit Pin multiple times.
Despite looking like it's flying above the ground, Pin is not immune to ground-based effects such as creep when doing its jumping attack. On the contrary, since every segment is guaranteed to pass over the damaging area, it can easily kill it in less than a second.

Gallery

Pin ingame.
Pin as one of Delirium's forms.
Concept art of a scrapped boss named "Pin, Trio," along with Mega Maw and what appears to be The Gate.

Trivia

Pin was added in the Wrath of the Lamb DLC for the original The Binding of Isaac.
The Frail is its posthumous version.
In the original Binding of Isaac, Pin had a Black Champion version that shot 6 normal shots instead of 1 exploding shot. This version of Pin doesn't spawn in Rebirth by default, but it still exists in the game's code and if somehow spawned (e.g. by modifying bosscolors.xml), it will work like in the original game. This can be achieved by adding any champion color variant in the bosscolors.xml file. If more colors are added, the mechanics will be applied to the color variant with the lowest number. For example, if colors 5, 8 and 12 are specified, the champion with color idx 5 will inherit these characteristics.
Pin is based off the pinworm, an internal parasite.
Pin is likely a reference to Lanmola, a boss from The Legend of Zelda: A Link to the Past; as nearly all attacks are the same.