Writhing Remains

The Writhing Remains is a pet item that can be dropped by Eater of Worlds in Master mode at a chance. It summons a pet Eater of Worms. It acts similar to The Deactivated Probe, which is the Master mode pet of The Destroyer. Curio: You can create a 3 tiles-long minecraft track with bumper ends. When you reach 40 mph speed, worm starts to fly around you wildly.

Trivia
The buff tooltip "May ruin several backyards" could possibly be a reference to worms digging many holes in backyards.