Poseidon

The Poseidon is a Hardmode spell tome that drops from the Giant Clam mini boss. It shoots a circular Poseidon typhoon sigil that homes in on enemies and lingers on top of them for a short duration, repeatedly dealing damage until it dissipates. Each Poseidon typhoon will pierce 3 to 8 times. Poseidon typhoons will also rebound off of blocks 9 times before disappearing.

Trivia

 * The name of the weapon is a reference to Poseidon, the Greek god of the Sea and other waters.
 * The shape depicted on the item and its projectiles resembles a trident, Poseidon's signature weapon.