Sacrificial Dagger

The Sacrificial Dagger is a Hardmode Summoner Banner that is sold by the Confused Zombie after the Wall of Flesh is defeated. On use, it summons a sacrificial dagger at the cursor's location that grants the player the Sacrificial Effigy buff while within proximity of it, indicated by a blue ring around it. The buff causes enemies killed by minion attacks to summon a helpful spirit. This spirit will assist the player by occasionally shooting spirit projectiles at nearby enemies, and will follow them for about 4 seconds before disappearing.

As with all summoner banners, only one can be active at a time; using another one will cause the sacrificial dagger to vanish.

Trivia

 * The Sacrificial Dagger could be a reference to the Ceremonial Dagger from risk of rain