Summoners are usable items that cause the summoning of certain NPCs or enemies. Most of the boss-summoning ones can only be used at night and/or under certain circumstances (e.g. in the Corruption, for the Eater of Worlds).

Worm Food

Mechanical Eye

Mechanical Worm

Guide Voodoo Doll

“The Suspicious Looking Eye is used to summon the Eye of Cthulhu boss. It can be crafted at a...

Suspicious Looking Eye

Mechanical Skull

Slime Crown

Old Man