The Scourge

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

Behavior
The Scourge floats quickly around the room, attempting to get above Isaac's position. It can perform the following attacks:
 * Shoots a large, fast cluster projectile out of its hood that homes in slightly on Isaac. When it hits a wall, it explodes into a spray of projectiles, leaving behind damaging Green Creep and a cluster of Small Maggots.
 * If The Scourge is below half health, it instead shoots out three slower, smaller cluster projectiles from out of its hood that create fewer projectiles on impact.
 * Launches one of its tendrils towards Isaac and embeds it in a wall. It then drags the tendril along the wall, causing projectiles, creep, and Small Maggots to shoot out from the wall.
 * Launches two tendrils and embeds them into the wall, one directly at Isaac and one in the cardinal/ordinal direction opposite of him. It then starts rotating its arms around while shooting two rings of 12 projectiles outwards.
 * Launches two tendrils to either side of Isaac, embedding them into the wall and trapping him in a triangle-shaped area. It will then perform one of two attacks:
 * Fires walls of tight projectiles with gaps to pass through from its body. It follows up each wave with an additional, faster projectile aimed directly at Isaac.
 * Fires horizontally travelling projectiles randomly out from both its left and right tendrils.
 * The three previous attacks end if The Scourge or its tendrils take enough damage.
 * The Scourge takes damage equal to 25% of the damage its tendrils take.
 * The tendrils passively take heavy damage if they're dragged along a wall, dealing a total of 50 damage to The Scourge for each tendril dragged.
 * The tendrils kill Small Maggots they are dragged into.
 * Moves to the center of the room and begins sucking in 2 tight streams of projectiles towards it in a spiral pattern. This spiral pattern can randomly switch directions during the attack. Additional random projectiles can appear in the gap between the two streams further limiting the space.

Trivia

 * The Scourge gets its name from a type of whip.
 * The Scourge resembles the Snapper monster, as they both attack using long, tendril-like whips, have a bottom row of teeth, and have an eye in the middle of their mouth.
 * It also resembles the Cultist monster, in terms of appearance.