Bloody Tear

The Bloody Tear is a consumable item used to summon a Blood Moon. It can only be used at night; attempting to use it during the day will not commence the Blood Moon and will not consume the item.

It is dropped with a chance by the Wandering Eye Fish, Zombie Merman, Blood Zombie, Drippler, Clown, Blood Eel, and Hemogoblin Shark, and with a  chance by The Groom, The Bride, and Dreadnautilus.

Trivia

 * The tooltip is a reference to Castlevania II: Simon's Quest, in which the game would show the same text whenever it became night. The name of the item comes from a track in Castlevania II known as Bloody Tears.