Alchemist is a NPC that spawns after beating EoC. He sells materials for potions and such and NPC base summoning potions. Currently supports the mods below.
Spawns after beating Eye of Cthulhu. Sells various buff potions (vanilla and modded). Also sells Fishing type potions after beating 5 fishing quests. Currently supports Thorium, Calamity, Spirit, Sacred Tools Tremor, MorePotions, UnuBattleRods, Tacklebox, Wildlife mods potions. Currently has 5 shops. All opening through game progression.
Spawns after beating Eye of Cthulhu. Sells various gems, chunks, including the ones from various mods (Thorium, Tremor, Spirit mods). Also has Arena Shop, in which he sells various stationary buffs and traps.
Young Brewer Edit
Spawns in Hardmode while both Alchemist and Brewer are alive. Sells various buff combinations, vanilla flasks and Thorium Coatings + Gas Containers. Has Calamity and Thorium mods support. All opening through game progression.
Can be force summoned by throwing Love Potion to Brewer and using special option in dialogue. Alchemist should be alive.
Spawns after beating Eater of Worlds\Brain of Cthulhu and if you have at least 5 other vanilla or modded NPCs. Sells various building and crafting blocks, crafting stations and various furniture. All opening through game progression.
Spawns after beating Eater of Worlds\Brain of Cthulhu and if you have free housing with Wing of the World placed inside of it. Sells various boss materials, EGO equipment and Treasure Bags (vanilla and modded) (if you have Expert World). Currently, has Thorium and Calamity mods support. All opening through game progression.
At death the drops "data module of AI" out with which help it is possible to create it anew.
If option CoinsDrop is set to true in Alchemistv7.json config file, then Treasure Bags can be bought by Reversity Coins of needed tier, whiv
drops from modded bosses.
If option CoinsDrop is set to false in Alchemistv7.json config file, then Treasure Bags can be bought by golden and platinum coins.
If option TreasureBagsShop is set to false in Alchemistv7.json config file, then Treasure Bags shops will not appear even in Expert World.
Doesn't spawn naturally by herself. You need to find the way for spawning her. It is related to Torn Notes, which are dropping from certain vanilla bosses. Message after beating Moon Lord for the first time and first GIF from #spoiler channel in Discord are giving advices too.
Sells Explorer's Brew, some materials for new ammo, recipes for special weapons and some ammo (if you have respective weapon in inventory).