Satan's Anvil

 was a limited time decoration available during the Stonecutters 2014 Event. It was seen in the game files months before the actual event.

Satan's Anvil was re-released as a premium item during the Clash of Clones 2014 Event.

It was re-released on January 10, 2017, during the Homer the Heretic 2017 Event costing 225 Donuts with a rebate of 100 Donuts.

About
Satan's Anvil is a desert located in Springfield where Lisa and the school visited. It is mentioned by Seymour Skinner that it is unknown why it is called this, although it is obvious to the viewer.

Trivia

 * An update on December 22, gave it a bonus payout.