Nightmare Catcher

The Nightmare Catcher is a craftable post-Moon Lord item used to summon the Abaddon, the Source of the Affliction boss. It can only be used at night. Attempting to use it outside of these conditions will have no effect and will not consume the item.

Trivia

 * The tooltip reads "Emissary of Nightmares", even though the boss' title was changed to the Source of Affliction. This is likely not intentional.