WANDERING TRADER

The Wandering Trader is a roaming, blue-robed merchant that is not a villager profession at all: it has no job-site block and no career tiers, and it buys only six kinds of item. It spawns on a timer near the player, typically every in-game day or so, arriving with two leashed trader llamas, and it despawns again after roughly 40 to 60 minutes whether or not you have traded with it.

Almost every offer is paid for in emeralds and gives you an item in return. Its catalogue is large but randomised: from a pool of 61 generic offers it shows five at a time, plus two picks from 15 rarer offers and two of its 6 buy offers. Prices range from as little as 1 emerald for fern up to 6 emeralds for blue ice, so it is most useful for gathering biome-specific plants, saplings, and decorative blocks you cannot easily reach.

Mechanically the Wandering Trader is unlike any job villager. It cannot be assigned a profession, it has no Novice-to-Master progression, and none of the usual tricks (curing, workstation re-rolling, or leveling) apply to it, because it never gains experience and its prices are fixed. It also never restocks: every offer has its own small number of uses, from a single sale for the potion of invisibility up to a dozen for the flowers, and once those are gone that is the end of it. The two trader llamas that follow it spit at hostile mobs but are otherwise just pack animals; killing either the trader or a llama drops a lead you can reuse.

The trader spawns naturally near the player on a recurring timer once your world has populated enough, appearing in a puff alongside its llamas regardless of the biome you are standing in. That makes it the only reliable way to obtain certain plants and saplings from biomes you have not yet visited, so it is worth checking its stock whenever one wanders into view rather than dismissing it out of hand.