Teratoma

The Teratoma is a craftable Pre-Hardmode item used to summon The Hive Mind boss in The Corruption. Note that the boss can also be summoned by killing a Hive Cyst, which spawns rarely in the Corruption.

It can be purchased from the Dryad for after The Hive Mind has been defeated.

Trivia

 * A "teratoma" is a tumor made of several different kinds of tissue, such as hair, muscle, bone, eyeballs or teeth.