Bloodworm

The Bloodworm is a critter found within the Sulphurous Sea after The Old Duke has been encountered once during the Acid Rain event. They can be caught with a Bug Net or Golden Bug Net. The Bloodworm acts identically to a Truffle Worm, fleeing from the player if they startle it. Bloodworms will not spawn if the Acid Rain is currently ongoing. Using a Bloodworm as bait in the Sulphurous Sea will summon The Old Duke as soon as the bait is caught.

It can be purchased from the Sea King for after The Old Duke has been defeated.

Trivia

 * The bait power's usage of the number 4 is a reference to the Chinese superstition about the mentioned number, due to it being a homonym for "death".
 * If the player attempts to summon The Old Duke using a multi-lined hook, such as the Early Bloom Rod, it will lead to multiple Old Dukes spawning in at once.
 * This is an homage to an oversight in Vanilla Terraria, where multiple Duke Fishrons can be summoned using a fishing exploit.
 * Similarly to the Truffle Worm, the Fisherman's Pocket Guide (and its combined accessories) will display a player's fishing power simply as "Warning!", due to the fact that The Old Duke will spawn when using this as bait in the Sulphurous Sea biome and no fish will be caught when not in the Sulphurous Sea biome.
 * Previously, the item's bait power was 69420%, as 69 and 420 are both numbers which are used in memes.