Cyborg

He shows up after Plantera falls, provided a vacant house is waiting. Nothing else gates him, so the only preparation worth doing is having the spare room built beforehand. Until he arrives there is no dependable rocket supply anywhere in the world, which means any launcher you picked up early has been sitting in storage doing nothing. He also sells a pylon like other vendors when he is settled and content in a biome, so think about where you put him rather than defaulting to the main base.

His basic ammunition is always in stock and cheap enough to buy by the stack and forget about. The stronger tiers are the ones to plan around, because they hang off conditions rather than progress: one appears only at night, one only while a Blood Moon is up, and the heaviest only during a Solar Eclipse. Treat an eclipse as a shopping trip as much as a fight, since the stock leaves when the event does and the next window may be a long way off. Dry rockets are the outlier, always available and priced like a specialty item, so buy those for a specific job rather than in bulk.

Clearing that invasion unlocks most of the rest of his list. Cluster rockets join the ammunition, with the heavier of the two limited again to a Blood Moon or an eclipse, so the same event planning applies. Two head pieces unlock next to them, neither of which has anything to do with launchers. Running the invasion before a big shopping trip rather than after it saves you a second walk.

Two more entries appear only while he is standing in a graveyard, and a graveyard is trivial to fake. Enough tombstones in one place and the biome forms. Neither line has anything to do with rockets, and the goggles in particular are the sort of thing people spend a long time not realizing they can simply buy. Set the stones up near his house, clear the whole list in one visit, then pull them out again, because nobody wants to live in one permanently.

The portal gun station reads as a post Moon Lord purchase, but the requirement is not really about progression. He offers it while you are carrying a portal gun or a station already, so one brought in from an older character unlocks it in a brand new world. That is the standard route to having a station network running long before the endgame.

A good chunk of his stock is not equipment at all. The drone, the racer and the goggles that go with them are a hobby set for building courses around your base, and the monoliths are lighting props for a room. None of it affects a run and all of it costs real gold, so leave that half of the list until you have money to waste.

Unlike most vendors he genuinely fights back. He answers nearby enemies with grenades, rockets and proximity mines, each behaving like the player weapon of the same name, and a mine he has left sitting undisturbed detonates for triple. A later patch made him considerably tougher and quicker to react as well, so a house on the outer edge of your base actually contributes during an invasion instead of needing a wall built around it.

Nearly all his possible names are Greek letters, a long running convention for robots in science fiction. The exceptions are the interesting ones: two nod at the developers, one is a Star Wars droid with the characters shuffled, and one points at Star Trek. His dialogue carries a Skyrim guard's complaint about a knee injury rewritten for a machine, plus a self referencing paradox. His bestiary entry credits the Mechanic and the Steampunker with building him, which sits awkwardly beside a line where he wonders aloud who the Steampunker is. Shimmering him changes how he looks and nothing else.