Duke Fishron

He is fished out of the ocean with a truffle worm on the hook. Cast, wait for the bob, reel, and he surfaces and hangs there for a moment before starting, invulnerable until the animation finishes. Time of day does not matter. What matters is that your bobber sits close enough to the world edge to count as ocean, and that the body of water is large enough to be treated as a proper lake.

The rules are looser than most people assume. Honey works, and so does lava, with none of the usual lava fishing requirements attached: any pole, no special accessory. He also demands nothing beaten first, so a stocked character can carry Truffle Worms into a brand new world and summon him there. Only one can exist at a time, and a sonar potion will not warn you that he is the thing on the line.

He gates nothing. Skipping him costs you no progression at all, which is exactly why he is the biggest optional shortcut in Hardmode. He hits like a post-Golem fight the moment Hardmode starts, and the gear he leaves behind flattens the next several hours: the mechanical bosses stop being a wall if you show up with his weapons. Killing him before the mechs is a real strategy rather than a stunt, and the payoff is out of proportion to the trouble.

The opening is a rhythm. He lunges in a straight line a fixed number of times, passing through blocks, then picks one of two ranged attacks and starts over. The first is a cloud of bubbles that drift after you and pop into a damaging burst, and the burst reaches further than the bubble itself, so clearing them at arm's length still hurts. Each one dies to a single hit from anything, and wind pushes them around. The second is a pair of bolts thrown down and outward that plant water tornadoes wherever they land, and each tornado spits sharks at you until it expires. The sharks can be shot down and cannot fly far.

At half health he stops, turns a darker green with glowing eyes, and comes back faster and harder. His armor drops, which is the one thing working in your favor. The lunges get quicker and there are fewer of them before he moves on, the bubble attack becomes a loop that trails a longer stream behind him as he flies, and the tornado attack becomes a single homing bolt that plants a much larger funnel directly under your feet. That last change is what breaks arenas: holding one position stops working, and the funnel throws roughly twice the sharks with more damage behind them.

On Expert and above he transforms again near the end. The sky fogs over, he turns invisible except for his eyes, drops his armor to nothing, and abandons every projectile. All that is left is teleporting and charging. It reads as chaos and it is not: he charges once, teleports to your other side, charges twice, switches again, charges three times, then resets. Count along and you can commit to the dodge before you can see where he is. He is the only boss in the game with three separate forms.

Expert and Master also give his hits a chance to leave you bleeding or bitten, one or the other but never both. The bite is the worse outcome, so a healing station and something that clears debuffs are both worth the inventory space.

The area he tolerates is generous sideways and tight vertically: stay near the world edge, keep off the ceiling, and do not drop below the surface layer. Leave it and he enrages, which doubles his damage and his armor, speeds him up, and cuts the pauses out of his rotation. It is not a soft penalty, it is the fight becoming unwinnable. Walling off the boundary or building the arena as a flat run across the water keeps you inside without having to watch for it mid-fight.

His charges aim at where you are rather than where you are going, so moving across him instead of away from him makes almost all of them miss. A zigzag is enough, and a dash from the Shield of Cthulhu, Tabi or Master Ninja Gear covers the rest. Platforms across the surface keep you from sinking, or Water Walking Boots do the same job with a slot instead of a build. An Inferno Potion is the neat answer to the bubbles, since the ring clears batches of them without you aiming at anything, and ichor or a Shine Potion makes him visible during the fogged phase.

He drops a spread of weapons plus wings, all of them a tier ahead of where you are likely to be, and his reforge costs are unusually low for that stage, so rolling modifiers on them is cheap. Nothing about the world changes when he dies and he unlocks no new content, but he is repeatable: another worm brings him straight back, which is the point, since you will want more than one of what he drops. If you die or run more than a few screens away he leaves and takes the summon with him, so bring spare worms. In zenith and remix worlds one of his drops is swapped for an older weapon, so check what you actually got.