The Rainmaker

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

Behavior
The Rainmaker floats slowly towards Isaac and performs the following attacks:
 * Creates two horizontal lines of 6 projectiles each on both sides of himself, then fires them towards Isaac.
 * Creates a ring of 12 projectiles around himself, then fires them towards Isaac in short staggered intervals.
 * Summons a large water projectile overhead, then pops it, unleashing a burst of projectiles in random directions.
 * Twirls around, following Isaac's movements while summoning projectiles which hover briefly before being fired towards Isaac.
 * At the end of this attack, the Rainmaker releases 8 projectiles in a radial burst.

Trivia

 * The Rainmaker's name is a reference to the traditional ritual of Rainmaking which may involve "Rain Dances".
 * The Rainmaker is apparently gay, according to a Tweet from Edmund Mcmillen.
 * This tweet also confirms that the Rainmaker is male.