Maw of the Void

Maw of the Void is an unlockable passive item added in The Binding of Isaac: Afterbirth.

Effects

 * +1.0 damage.
 * After firing tears for 2.35 seconds, releasing the fire button unleashes a black ring around Isaac that expands and contracts, dealing damage at a rapid rate to all enemies touching it.
 * The charge is completed when a red upside-down cross appears on Isaac's forehead.
 * With charge bars enabled, there is also an indicator that displays the charge.
 * The black ring deals damage equal to Isaac's current damage per tick, and ticks a total of 30 times. It lasts ~1.97 seconds (118 frames).
 * Enemies killed by the black ring have a 5% chance to drop Black Hearts.
 * Black Hearts will drop as soon as the enemy is killed. (In other words, the heart will drop at the beginning of the death animation rather than at the end of the death animation.)

Synergies

 * Guppy: Damaging enemies with Maw of the Void allows flies to spawn from the Guppy transformation. Flies are spawned at a rate of approximately one fly per tick of damage for each enemy it hits. This causes a lot of flies to spawn very quickly. The spawned flies will also move to attack the nearest enemy immediately.
 * Homing tears: The ring curves towards enemies.
 * : Massively increases ring damage and poisons enemies.
 * The ring also explodes on enemy or obstacle contact.
 * : The ring sends out electric currents when it hits something.
 * : Ring can destroy projectiles.
 * : Occasionally spawns a pool of creep where the ring makes contact with an enemy.
 * /: Ring obtains knockback effect.
 * : The ring is much larger and deals 1.5x damage per tick.
 * The ring is larger but deals normal damage.
 * No effect.
 * : Ring attracts pickups and enemies towards it.
 * Wiggle Worm: The ring has wavy edges.

Interactions

 * : Tear must be moved before the ring activates.
 * : The ring damage is halved.
 * The ring deals normal damage.
 * : Crosshair must be moved for 4 seconds before the ring activates.
 * While firing, the ring charges automatically and activates immediately upon full charge.
 * : No effect on charge time but massively reduces damage.

Trivia

 * Maw of the Void has a unique charge bar, filling with red instead of the usual green, as well as having a small swirl reminiscent of its shape in the middle of it.