I have to admit that the inspiration for this class is largely not my own and came from an entry in Dragon Magazine #2. I simply fine-tuned the mechanics from OD&D to lotfp/basic.
Bubbling brews, explosive extracts, and catastrophic concoctions. These are the creations of the alchemists.
Alchemists are steeped in the mysticism of their age while utilizing a form of rudimentary science. They're goals aren't to understand the world but to bend it to their will. They desire a means to convert base metals into gold, to cure any disease, and to defeat death itself. All of which seem like impossible tasks. But for Alchemists it's not a matter of if they will accomplish such feats, its a matter of when.
Despite all logic alchemists are capable of throwing together an assortment of mundane materials (represented by coin) to produce otherworldly concoctions, mostly in the form of potions. However they are capable of crafting much more than liquids. Bombs, fire, pills, and more is at the alchemists' finger tips.
Alchemists have the hit dice, experience track, and saving throws of a Specialist/Thief/Rogue. After all alchemists are simply ordinary people with a deep specialization in the craft of alchemy.
Poisons: Alchemists can brew poisons of a strength level equal to their HD or lower. Crafting a poison costs 50sp per strength level and takes a whole day.
Sedatives: Sedatives function as poisons but if the poisoned creature fails their saving throw they fall unconscious for d4 hours instead of dieing horribly. Another key difference is that they cost 100sp per strength level to craft but still only take a day to make.
Bombs/Fire/Acid: These defensive implements deal d6 damage per strength level. They have a range of 10'/20'/30' and a blast/splash radius of 5 feet. Alchemists add their intelligence modifier to attack and damage rolls with their bombs. (This represents their fine-tuning.) Creatures caught in the radius take minimum damage and can save for half damage. Lastly, bombs cost 100sp per strength level and take a whole day to craft.
Potions: Potions cost 200sp per strength level to make and have a duration of d4+strength level. The number of potions alchemists can make in a day depends on the potions per day chart. (See Potions per day below.)
First Level Stuff: From the onset of their journey, alchemists know three random potions from the level one potions list. When alchemists gain a level they learn a new random potion that they are capable of crafting.
Potions per day: Alchemists' potion per day chart is equivalent to a clerics spells per level chart minus seventh level entries.
1. Heroism: As the Heroism spell
2. Giant Strength: The imbiber becomes as strong as a giant, dealing double weapon damage, and gains the ability to throw boulder-like objects (3d6 damage).
3. Animal Control: The imbiber gains the ability to relate to, understand, and manipulate the emotions of animals of one type. Animal types include Avian, Fish, Mammal, Amphibian, and Reptile.
4. Water Breathing: as the Water Breathing spell.
5. Healing: The imbiber regains 1d6+1 hit points. It also cures paralysis.
6. Purification Powder (10): When sprinkled on spoiled rations or water makes them fit to consume. Will not neutralize poison. Serves 10.
7. Flash Pellets (5): A small pellet which explodes on hard contact. Anyone in eyeshot must save vs Paralyzation or be blinded.
8. Dust of Sneezing (10): If thrown at the face, this dust causes a violent fit of sneezing, inflicting a -4 penalty, if the victim fails a save vs Poison.
9. Oil of Slipperiness: Any creature or object coated in this oil can't be restrained or grabbed. If a floor is coated any individual standing, walking, or running on the floor will fall unless they save vs Paralyzation.
10. Tanglefoot Pills (2): A small synthetic fungoid which rapidly expands to fill a 10'x10' area with rubbery tentacles. It has 9+strength level hit points and an AC of 15.
1. Speed: As the Haste spell.
2. Levitation: As the Levitate spell.
3. Growth: The imbiber doubles in size and deals double damage.
4. Diminution: The imbiber shrinks to 6 inches tall.
5. Human Control: The imbiber gains a one-time use of the Charm Person spell for the duration.
6. Plant Control: The imbiber is able to control plants and plant-like creatures within an area of 20 feet squared, to a distance of 90 feet. Plants and plant-like creatures can obey commands to the best of their capacity. For instance, vines can be controlled to wrap around targets, and intelligent plants can be given orders. However, intelligent plant beings receive a saving throw versus magic.
7. Dust of Appearance (10): This fine powder appears to be a very fine, very light metallic dust. A single handful of this substance flung into the air coats all objects within a 10' radius, making them visible even if they are invisible. Makes 10.
8. Dust of Paralyzation (10): Similar to the Dust of Appearance, but creatures coated in the dust must make a save or be paralyzed.
1. Superheroism: As the Heroism spell but the duration is doubled.
2. Polymporh: As the Polymorph Self spell. The type of creature turned into is specified when the potion is crafted.
3. Fire Resistance: The imbiber is impervious to all forms of ordinary flame. Damage caused by magical flame is reduced by -2 per damage die and if a saving throw is required the imbiber makes his save at +2.
4. Extra-Healing: The imbiber regains 3d6+3 hit points. Unlike a Healing potion, this potion can be imbibed on three separate but equal occasions to regain 1d6+1 hit points.
5. Fly: As the Fly spell.
6. Clairvoyance: As the Clairvoyance spell but the imbiber cannot hear.
7. Clairaudience: As the Clairvoyance spell but the imbiber cannot see.
8. Dust of Sneezing and Choking (15): As the Dust of Sneezing but if the victim fails their save they will die when the duration is over.
1. Invulnerability: The imbiber gains +2 to his armor class and all saves for the duration.
2. Undead Control: As the Mass Charm Person spell but it only effects undead creatures.
3. Giant Control: As the Charm Person spell but it only effects Giants.
4. Immunization from Lycanthropes: Protects the imbiber from contracting lycanthropy for one month. There is a 1-in-100 chance he will contract the disease from this potion.
5. Invisibility: As the Invisibility spell.
6. Homunculi Creation: As the Find Familiar spell.
1. Dragon Control: As the Charm Person spell but it only effects dragons.
2. Gaseous Form: As the Gaseous Form spell.
3. Treasure Finding: The imbiber can sense any treasure within 240 feet containing valuable metals or gems.
4. Dust of Disappearance (20): As the Dust of Appearance except those covered by this dust turn invisible.
5. Oil of Etherealness: As the Oil of Slipperiness but anyone coated in this oil turns invisible and can pass through non-ethereal objects.
6. Cloning Culture: As the Clone spell.
1. Longevity: The imbiber is made 1d12 years younger.
2. Cure Disease: As the Cure Disease Spell.
3. Regeneration: The imbiber of this potion regenerates 1 hp per round for an entire day regardless of the potion's strength level. Also this potion functions as a Resurrection spell if applied to a corpse. Additionally it can regenerate lost limbs if applied to an inactive character over a two week period.
4. Mind Dump: The imbiber is immune to psionic location or attack.
Research and Poison
I've left mechanics for poison and research absent on purpose because in my experience the system for either depends on the referee in question.
I personally use the poison rules from Dragon Magazine #2 in my games.
As for research I use a modified version of Last Gasp's research rules.