The Lily-of-the-Valley is a Hardmode accessory which has a 33% chance to drop from Medicine Melancholy. It causes the wearer's melee attacks to inflict the Toxin debuff on enemies. In addition, minions which inflict their damage via melee attacks (rather than attacking from range) will also inflict Toxin.
Enemies afflicted with Toxin will lose 8 health per second. When used in PvP, players afflicted with the debuff will also have their light vision severely reduced.