Duke Fishron

Duke Fishron is a Hardmode Boss. He is immune to the On Fire!, Poisoned, Venom, and Frostburn debuffs. He will always drop exactly one of his five weapons at a 20% drop chance for each; the Fishron Wings, Mask and Trophy are dropped independently, however.

Summoning
Duke Fishron is summoned by casting a Fishing Pole into one of the two Oceans while having a Truffle Worm in the player's inventory to use as Bait. The Truffle Worm is a rare Critter that must be caught with the Bug Net in an underground Mushroom Biome.

Summoning Duke Fishron does not require that any other bosses have been defeated beforehand, but a world must be in Hardmode in order to obtain the Truffle Worm used to summon him.

First stage
Duke Fishron lunges at the player exactly five times, traveling through all blocks, before using one of two projectile attacks:


 * Detonating Bubble: Duke Fishron blows roughly 10-20 bubbles from his mouth that follow the player at moderate speed, exploding and dealing damage on contact. These bubbles can be destroyed via any attack or projectile, however they can be hard to hit.


 * Sharkron: Duke Fishron waves his fins, summoning liquid blobs that fall (bypassing any platforms) until they travel 1.5x the vertical size of the screen or impact with blocks. They then spawn Sharknadoes: giant water tornadoes that each fire several Sharkrons. The Sharkrons have limited flight range, are destroyed on impact with blocks, and can be killed by the player.

After firing a Razorblade Typhoon, he lunges another 5 times, beginning the cycle again.

Second stage
When Duke Fishron falls below 25,000 health, he remains stationary for a second and his eyes glow. His damage and speed increase significantly, but his defense is reduced to 40. His lunges become faster, and are only performed three times instead of five before executing one of his projectile attacks, which are also upgraded:


 * Detonating Bubbles are now fired while Duke Fishron flies in quick loops, which leave a trail of the bubbles behind.
 * There is now only one "blob" that causes the tornado, but it follows the player, creating a "Cthulhunado" (upgraded version of first stage's "Sharknado") on contact. The blob itself does not cause damage, but will spawn twice as many Sharkrons as in the first stage.

Third stage (Expert Mode Only)
When Duke Fishron falls below 10% of his maximum health, the sky will be shrouded with a thick, blue fog. Everything, including Duke Fishron, becomes barely visible within the fog, but still can be located using the minimap, or his small yellow eyes. While the fog is active Duke Fishron reaches maximum speed, and begins to teleport and dash in order to hit you.
 * After each dash, there is a small pause.
 * He teleports in front and slightly above of the player, making running away impossible.

Tips

 * Trying to run away from the Ocean Biome isn't recommended, as the boss will start lunging at the player continuously, dealing high amounts of damage and almost instantly killing the player in most cases. This behaviour is similar to Plantera's, who will enrage if the player were to leave the Underground Jungle.

Trivia

 * Duke Fishron was part of an April Fools joke by Terraria staff that claimed an "Aquarian Horde" event was to be included in the game. The Duke Fishron element alone ended up actually being introduced.
 * His Sharknado attack is a nod to the 2013 movie Sharknado.
 * Duke Fishron turns transparent when over blocks, much the same way that Pigrons do.

History
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