Alchemist

Alchemists were proto-chemists who worked in the medieval and early modern periods (and a few even survived into the Age of Enlightenment; Newton in particular is sometimes mocked for believing in alchemy) in Europe and the Islamic World. Like modern chemists, they thought matter followed specific rules and would reliably change at different heats, proportions, etc. Unlike modern chemists their rules were rather... derpy. They thought, for instance, that examining an object physically would reveal its internal properties, and spent lots of time in chemically useless pursuits like trying to find phlogiston, a hypothetical chemical that was attributed to be responsible for combustion, or, most famously, trying to turn lead into gold. A similarly-derpy tradition in Asia revolved around making various potions, most notably their quest for the legendary elixir of immortality which mostly yielded a plethora of potions of mortality, since they thought the primary ingredient was the highly-toxic element of mercury. Alchemy was basically an attempt at outright magic before it got distilled into modern day chemistry. Nonetheless they did stumble upon a few useful ideas, like gunpowder.

In the modern age, they're generally thought of as bumbling primitives at best and devious charlatans at worst, but they played an important role in keeping science alive in an age where research wasn't much of a thing and providing by accident some useful information for chemists. Also many of their experiments can be considered metaphorical, and the close attention they paid to exotic chemical reactions were often guided meditations which were intended to have lasting psychological effects of the observer. Like astrologers, they were often conmen, but some of them were highly skilled, intelligent, and poetic.

AD&D

The alchemist appeared in Advanced Dungeons & Dragons as a specialist option for the wizard, debuting in "Player's Option: Skills & Powers" before being reprinted in "Player's Option: Spells & Magic". Thematically, they are described as a scientist-wizard, similar to yet distinct from the Artificer - alongside its fellow Skills & Powers specializations, the Geometer, Shadow Mage and Song Mage, it was classified as a "Thaumaturgical Specialist" in Spells & Magic, gaining kindred in the form of the Artificer and the Wild Mage, but losing the Shadow Mage as a sibling; it was rebranded as an "Effect Specialization" in this book.

Functionally, they're a Transmuter who trades the bonus potency with transmutation spells for the ability to brew potions.

Mechanically, this specialist wizard has the following traits:

Minimum Ability Requirements: Intelligence 15, Dexterity 14

Permitted Races: Human, Half-Elf, [[Gnome

Prohibited Schools: Illusion, Necromancy

An alchemist can memorize 1 additional Alchemy School spell per spell level.

An alchemist receives a +15% bonus to learning spells from the School of Alchemy, and a -15% penalty to learning spells from any other school.

An alchemist automatically learns a spell from the School of Alchemy whenever he reaches a new spell level.

When attempting to create a new School of Alchemy spell, the alchemist treats its spell level as being one level lower.

Lab-Bound: An alchemist starts play with an alchemical laboratory, which requires 50 gold pieces a month to represent stocks of reagents, replaced equipment, and so forth. Building a new laboratory costs 1,000gp per character level. Without access to their lab, an alchemist cannot memorize their bonus daily spells, conduct research, make potions, or add new spells to their spellbook.

Potion Brewer: From 6th level onwards, an alchemist can learn formulae for magic potions. This uses the mechanics for researching a spell, treating the potions level as equal to its XP value divided by 100. Research time is 2 weeks per effective spell level, and it costs 500gp per effective level. The alchemist must pass a Learn Spells check to learn a potion formula, and the number of potion formulae an alchemist can learn is the same number as their maximum spells per level score; it is also affected by Intelligence, rising or falling in the same way. Once an alchemist has learned a potion formula, they can brew doses of the formula at will, but this requires the expenditure of 3d6*100 gold pieces and a week's work in the lab for each dose - not to mention they need to pass a Learn Spells check to successfully brew it. In "Spells & Magic", the alchemist is stated to gain a +1% bonus per character level to this "brew potion check".

Reagent Focus: When an alchemist casts spells labeled "School of Alchemy", they have no verbal components.

School of Alchemy Spells (from "Spells & Magic"):

• Affect Normal Fires (1st)
• Fire Burst (1st)
• Grease (1st)
• Metamorphose Liquids (1st)
• Patternweave (1st)
• Protection from Evil/Protection from Good (1st)
• Fool's Gold (2nd)
• Glitterdust (2nd)
• Melf's Acid Arrow (2nd)
• Pyrotechnics (2nd)
• Sense Shifting (2nd)
• Stinking Cloud (2nd)
• Alamir's Fundamental Breakdown (3rd)
• Flame Arrow (3rd)
• Melf's Minute Meteors (3rd)
• Protection from Evil, 10' Radius/Protection from Good, 10' Radius (3rd)
• Solvent of Corrosion (3rd)
• Enchanted Weapon (4th)
• Fire Charm (4th)
• Fire Trap (4th)
• Vitriolic Sphere (4th)
• Cloudkill (5th)
• Fabricate (5th)
• Rusting Grasp (5th)
• Transmute Rock to Mud/Transmute Mud to Rock (5th)
• Vile Venom (5th)
• Death Fog (6th)
• Glassee (6th)
• Stone to Flesh/Flesh to Stone (6th)
• Transmute Water to Dust/Improved Create Water (6th)
• Acid Storm (7th)
• Hatch the Stone from the Egg (7th)
• Neutralize Gas (7th)
• Statue (7th)
• Glassteel (8th)
• Incendiary Cloud (8th)
• Crystalbrittle (9th)
• Glorious Transmutation (9th)

Pathfinder

Pathfinder alchemists are basically a mad scientist character class. They cackle, they drink mutagen and turn into the Hulk, they make construct-soldiers out of dead bodies, they cast spells by chugging potions, you get the idea.

Mechanically, Alchemists get three tricks. The first are alchemical bombs, which are splash weapons that they can prepare a certain number of per day. The second are infusions, which are bottles of magic that are prepared like Wizard spells but drunk like potions. The third is mutagen, which is basically Mr. Hyde juice; mechanically, it buffs one of your physical stats at the expense of your mental stat, and too much stat damage will cause sudden reversion.

Alchemists are a lot of fun, since they get throw anything as a power and have lots of unique bombs they can make, and actually make "incredible discoveries!" as they level up, ranging from growing new limbs and tumors that fall off and act as familiars to learning how to cheat and bottle spells they shouldn't theoretically have. There's nothing else in the game quite like them, and it makes them unique and interesting. Unfortunately, all those powers aren't terribly focused, which is a downer. If you want to build a decent alchemist, pick one or two of their mechanics and leave the third by the wayside. Oh, and everyone will hate you if you don't take the discovery which lets other people use your infusions, which you should do anyway, because what else are you going to do with that enlarge person potion? Wade into melee? My 30+ AC, 3 Nat attacks a round, and +12 to Hit suggest that that is a good idea as long as the mutagen holds.

Also, they're very selfish casters that need to take a discovery just to let other people imbibe their spell-potions, and without cantrips they can only identify potions without spending spell slots. As a result, they aren't the best solo-casters in a party full of melee beatsticks.

If you want a hilariously awesome class that does things you haven't necessarily seen before in the d20 system, pick this guy. If you want something a little more geared towards optimized mechanical play? I'm sure they'll have another overpowered wizard prestige class/archetype/pile of new spells ready for you in the next splatbook, you damn munchkin-robot.

5e

Alchemists were relased as one of two subclasses (the other being the gunsmith) for the Artificer Class in an Unearthed Arcana article.

The Classes of Pathfinder 1st Edition
Core Classes:	Barbarian - Bard - Cleric - Druid - Fighter - Monk Paladin - Ranger - Rogue - Sorcerer - Wizard
Advanced Player's Guide:	Alchemist - Antipaladin - Cavalier Inquisitor - Oracle - Summoner - Witch
Advanced Class Guide:	Arcanist - Bloodrager - Brawler - Hunter - Investigator Shaman - Skald - Slayer - Swashbuckler - Warpriest
Occult Adventures:	Kineticist - Medium - Mesmerist Occultist - Psychic - Spiritualist
Ultimate X:	Gunslinger - Magus - Ninja - Samurai - Shifter - Vigilante