Duke Fishron

Duke Fishron is a Hardmode boss that is summoned at the Ocean Biome. It is immune to the On Fire!, Poisoned, Cursed Inferno, and Frostburn debuffs. To summon this boss you first need to obtain the Truffle Worm. After obtaining it, go to the west or east ocean (it doesn't matter which one), and then cast any Fishing Rod into the ocean, with the Truffle Worm as the bait. When you get a bite, reel it in, and Duke Fishron will spawn and attack you.

Duke Fishron cannot spawn randomly like most bosses, he must be lured in like so:
 * Hardmode must be active
 * Catch a Truffle Worm with a Bug Net in an underground mushroom biome
 * Use it as bait and fish as you normally would and Duke will appear
 * You must fish for him in an ocean biome or he will not spawn and your hard-earned Truffle Worm will be wasted on a useless catch.

Duke Fishron, unlike the other hardmode bosses, goes in the same category as Queen Bee and King Slime, meaning he doesn't have to have had another boss be fought to gain access to him(like Mechanical Bosses -> Plantera -> Golem for example), and it is not required to fight him to progress farther in the game. He is however the hardest in the game.

Behavior
Duke Fishron looks like a fanged pig mixed with a ginormous fish, with many fins and a fishtail. Despite being a non-required boss, he has 11000 more health than the "last boss in the process" so far, meaning he is the hardest boss in the game.

Despite being a fish, he flies and goes through blocks like most bosses, so don't underestimate him. Once you see the message "Duke Fishron has awoken!" he will rush out of the water like a rocket with a green light trail behind him and go strait for you. As said before, he is able to fly, so his main attack is similar to the Eye of Cthulu or the Twins, charging at the player constantly.

His secondary attack is - referencing a commonly criticized movie - Sharknado. Yes, that's right, his second attack is to activate a large water spout that is teaming with sharks and is constantly tossing the player around.

at 50% health goes enraged gaining attack and speed