The Visage

The Visage is a boss added in The Binding of Isaac: Repentance that can appear in.

Phase 1
The Visage is bound together by a chain and cannot be damaged; the chain must first be destroyed to progress the fight, and has 150 health. During this phase, it only has one attack:
 * The heart slowly wanders around the room, and the mask attempts to move toward Isaac, constrained by the length of its chain (which reaches up to 4 tiles outward). Occasionally, the mask charges at Isaac when he approaches it from any cardinal direction, predicting his movements. Upon colliding with a wall, the mask launches out a spray of rock projectiles before being pulled back to the heart.
 * The mask cannot charge if it’s close to Isaac.
 * The chain only extends for this attack, it's normally rigid and constrains the mask and the heart to a specific length.
 * If the mask hasn’t charged in a while, it starts pulling the heart with it in its attempt to reach Isaac.

Phase 2
Once the chain is broken, the mask and heart are unbound from each other and their behavior changes:
 * The mask freely moves around the room, briefly speeding up and chasing Isaac if it sees him in a cardinal direction.
 * The mask can be damaged by explosions, piercing shots, or by being shot in its open back. The mask itself has 100 health and deactivates when defeated, which stops it from moving, dealing contact damage to Isaac, or from firing certain projectiles when used by the heart. However, it can still block Isaac's tears.
 * The heart now actively avoids Isaac, but also uses a chain to perform a variety of attacks in conjunction with the mask:
 * Launches a chain to the mask. Once attached, it directly pulls the mask in and fires a horizontal helix of lasers that pushes both backwards into a wall.
 * The lasers and pushback don’t happen if the mask is deactivated.
 * Launches a chain to the mask. Once attached, it swings the mask around in a spiral while also bringing the two closer. The mask fires purple projectiles outward while being reeled in. If the mask collides with wall before it unites with the heart, it creates rock projectiles on impact and is then pulled directly to the heart.
 * The mask doesn’t fire projectiles while being reeled in if it’s deactivated.
 * Launches a chain to the mask. Once attached, it directly pulls the mask in and then jumps onto Isaac's position, creating a burst of rock projectiles as well as 4 rock waves in the diagonal directions upon landing.
 * Launches a chain at Isaac. If the chain hits him, it pulls him into the heart, causing him to take contact damage. If the chain misses, it pulls the heart into the wall it hits, creating a burst of rocks and purple projectiles. This attack can only be used if the mask is deactivated, and greatly prefers using it if can.
 * Unlike all other attacks, the chain directly hitting Isaac doesn’t deal damage, only him being pulled into the heart.
 * If the chain hits a bomb while being launched, the bomb instantly explodes and the attack is cancelled.

Phase 3
When the heart drops to half health, its visual outer shell breaks, exposing the heart. The Heart's movement becomes quicker and more erratic along with an attack change: Once the heart has been killed, the mask permanently deactivates.
 * Launches a large, slow-moving energy ball known as Visage Plasma in a diagonal direction that bounces off of walls. If this projectile touches the mask, it fires a laser out its back, rapidly propelling it in the direction it was facing and creating rock projectiles and a radial burst of 8 projectiles upon collision with a wall.
 * If the mask is deactivated, Visage Plasma will automatically travel towards it, reviving it as well as causing its normal effect.
 * Visage Plasma have 50 health, and can be destroyed by Isaac.
 * The heart always begins the phase with this attack.
 * Briefly stops moving and fires out a ring of 16 purple projectiles.
 * If there are 3 Visage Plasma floating around the room, the heart sucks them in, drawing in Isaac in the process. Each Visage Plasma absorbed heals the heart a small portion of HP. After absorbing all 3, it fires out 4 tight rings of fire along with 4 short-range diagonal lasers.
 * The mask deactivates during this attack, regardless of its HP. Unless the heart is on a far side of the room and Isaac is far away enough, Isaac must hide behind the mask to dodge this attack as the rings of fire are too dense to weave through.

Trivia

 * The Visage started as a boss versus screen mockup by Antibirth artist NotYourSagittarius in January 2015, alongside Reap Creep and a scrapped posthumous version of Dingle known as "The Mass".
 * The Visage appears to be a fiery variation of the Mask of Infamy.
 * In a way, it can be seen as the posthumous version of the Mask of Infamy.
 * The Visage in Antibirth bore a grey and purple color palette better suited for, while the Visage in Repentance has been recolored black and red to match the floor. Many of its attacks still remain purple.
 * The back of the mask shows many small children being burned while the mask is alive.
 * This is probably a reference to the fact that in Gehenna, some kings of Judah sacrificed their children by fire.
 * In Antibirth, instead of many children, there was a singular Isaac head in the back of the mask.
 * This is a reference to the original Mask of Infamy from the Wrath Of The Lamb DLC of the original flash game, as it had a small head peeking through the crack behind the boss.