The Scourge is one of the bosses that can appear in the Corpse.
The Scourge has several attacks:
Sucks in red tears from across the screen.
Clings one of its arms to the wall, moving it across half of the wall while spewing out small maggots and green bullets which leave creep.
Clings his arms to walls and then starts rotating them while firing rings of bullets outwards.
Pins his arms to the walls, trapping the player in a triangle-shaped area. He will then attack in one of two ways.
Waves of bullets will fire from the left and right sides. Each wave has holes in it, but once the two waves meet in the center, the holes in the right wave will be filled by the bullets in the left, and vice versa.
Fires tightly packed waves of bullets from his main body that generally only have one small hole to dodge through.
Fires a bullet cluster at Isaac that explodes into smaller clusters and Small Maggots.
Damage done to him through his arms is reduced by 90%.
The Scourge resembles a boss version of a Snapper, especially considering that both use long extendable limbs with spiked tips.
The Scourge, in keeping with the naming conventions of the monsters it's based on, is named after a specific kind of barbed whip.