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 large 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 with a green light trail behind him and go straight for you. Duke Fishron has two phases. 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. He will do this 5 times before swithing to Two different moves.

Phase One He will lunge at the player 5 times before initiating another attack. One of these attacks are blowing explosive bubbles from his mouth, roughly 20. These bubbles will follow the player around at a reasonable speed and deal damage upon touch, also busting the bubble. These bubbles can be destroyed by any kind of attack or projectile. After blowing his bubbles he will once again lunge at the player 5 times before doing another attack. His other possible attack is - referencing a commonly criticized movie - Sharknado. First off he will wave his fins once, then water-like blobs will fall to the ground, bypassing any placed platforms, which is useful in an arena. Once these 2 blobs have touched the ground, they will form a tornado, which can damage the player. These tornado's will spawn several fish which will charge at the player. These fish do not go up forever, as they will fall down once a "jump height" has been reached. At 25000 HP he will be stationary for a second, then he will become enraged and get glowing eyes.

Phase 2 At this point he gets extra attack, speed and defense (unconfirmed), and getting a direct upgrade from both his secondary moves. His lunge will however stay the same. He no longer will blow bubbles from his mouth, as he will fly a in a circle about 3 times, leaving the exploding following bubbles. His sharknado attack is also upgraded, as that the blobs will now follow the player, creating a tornado when they touch the player. These blobs will not inflict any damage. However, they will spawn about twice as much fish as in the previous tornadoes. This will go on until Duke Fishron has been defeated.

Recommended for this fight are items that will increase your speed. The Hoverboard is quite useful to dodge his charging attack by just moving sideways, then down, then the other way again and so forth. Never stop attacking the boss at all times to make sure all the bubbles he blows pop. This boss is easier to do with other people, as soloing Duke Fishron is not an easy challenge.