An "IOU" (abbreviation for "I owe you") is a document stating one's debt to another. In the case of this item, the debt is a drop from The Leviathan.
Despite the Siren and Leviathan dropping their weapons after the Wall of Flesh had been defeated at the time it existed, Living Shards from Plantera were required to turn IOUs into the boss' various weapons.
This page was last edited on 16 October 2020, at 19:29.
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