Truffle Worm

It lives underground in glowing mushroom country, and the requirement is looser than it sounds. Mushroom grass alone is enough. You do not need the full hundred tiles that make the game call an area a proper biome, so a patch of mud seeded in the underground jungle already produces them. Most spawns on mushroom grass come out mushroom themed, and a decent slice of those roll as the worm rather than a spore or a fungi enemy. It gives off a faint light of its own, which is often the first thing you notice.

The usual critter trick of parking town NPCs nearby does nothing here. What helps is the opposite. Every enemy already alive cuts into the chance the next spawn happens at all, so clearing the fungi and spores hanging around your farm directly raises your odds. A Water Candle and a Battle Potion push the rate up from the other side, and Luck feeds into it too.

The rest is layout. Convert a wide section of underground jungle with Dark Blue Solution, or take the slow road and scatter Mushroom Grass Seeds across plain mud. Then make yourself leave and come back, over and over. A pair of teleporters with hoiks, or a Portal Gun loop, gives you an endless fall through the farm, and if you drop far enough everything else despawns behind you, which clears the queue for the one you actually want.

It knows you are there. Stand near one for about a second and it dives into the ground, and once it goes offscreen while burrowing it is deleted on the spot. Speed is the whole skill. A dash from Tabi, Master Ninja Gear or the Shield of Cthulhu closes the distance in time, though the shield deals damage and can kill the worm outright. Wings, a good hook or Lightning Boots do the same job more safely, and a Rod of Discord removes the problem entirely.

A Golden Bug Net reaches further and swings quicker than the plain Bug Net, which converts a lot of near misses. You can still net one mid burrow, so a worm dropping into a pit you cannot reach from above is catchable by getting into the cave underneath and swinging up as it comes down. If it falls like an ordinary enemy instead of digging, it follows normal despawn rules and you can chase it much further. Watch your minions as well: they will not target it, but a stray hit still kills it.

Carry a Lifeform Analyzer. It calls the worm out by name, and because enemies despawn at a greater distance than the analyzer can see, a ping tells you roughly where to search rather than only that one exists somewhere. Without it you walk past most of them.

It baits exactly one thing, only from the Ocean, at any hour of the day or night. Cast it into any other water and the bobber sits there indefinitely, no bite and no consumption. When it does work the worm is gone regardless of what you have equipped, since the Tackle Box and its upgrades save ordinary bait and do nothing for this. The Fisherman's Pocket Guide gives up entirely and prints a warning where the fishing power reading normally goes.

Bring more than one. Duke Fishron rarely dies on the opening attempt, and the walk back to the mushroom biome between tries is the most tedious part of learning that fight. A caught worm sits safely in your inventory for as long as you like and takes no damage from anything hostile, and you can release it again later or turn it into a cage for display. The cage is a one way trip unless you decraft it in Shimmer.

• Its listed bait power is a nod to the number of the beast, which suits an item whose only purpose is calling up a sea monster.
• Truffle plus worm mirrors the pig and fish that Duke Fishron is built from. Pigs have been used to sniff out truffles for centuries, and the game keeps circling the gag: the Truffle himself complains about a relative losing a leg to one, and both the Pigron and Cute Fishron mounts are summoned by truffles.
• It is classed as an enemy yet cannot hurt you at all, a very short list it shares with the Windy Balloon, the Lunatic Devotee and the Prismatic Lacewing.