The alchemist is a scholar obsessed with the material world around them. They study the secrets of metallurgy, of herbalism and potion crafting, and of the properties of all manner of different compounds and substances and how they react to each other. The ultimate goal of such study is two fold: to unlock the secrets of life itself, what it is that turns dead matter into living creatures, as well as the mastery and control over substances, most often metals, to manipulate them to create fantastic results. The result is a true mastery of the physical world.
Starting at 3rd level when you choose this archetype you gain proficiency with alchemist's supplies if you do not have it already. If you are already proficient with them, you gain proficiency in another tool of their choice. You also gain an expertise die on checks made with alchemist's supplies. At level 7, this die increases to d6. At 10, it increases to d8 and your maximum size of an expertise die on checks with alchemist's supplies increases to d10. At level 14, this die increases to a d10 and your maximum size of expertise die on checks with your alchemist's supplies is d12. You may always choose to use Intelligence on checks with alchemist's supplies.
In addition, you add Hardy Adventurer to your list of bonus feats.
Also at 3rd level, you only need to spend half the normal amount of time and gold in base materials to craft potions.
Also at 3rd level, you gain proficiency with attacks made with acid flasks, alchemist's fire, and flash bombs. Furthermore, each of these is more potent if crafted by you.
At 7th level you are proficient with poisoner's kit if you are not already. You have resistance to poison damage and advantage on saving throws against poison damage. You may also apply an injury poison to a piercing or slashing weapon as a bonus action rather than an action. In addition, poisons you craft can use either their normal DC or your scholar DC, whichever is higher.
At 10th level you gain the ability to create a homunculus. This requires 8 hours of work and 2000 gp of reagents. It also requires you to shed some of your blood, dealing between 2d4 and 12d4 piercing damage chosen in multiples of 2d4. This damage cannot be reduced by any means, and your maximum hit points are reduced by this amount until the homunculus is destroyed. The homunculous uses the stats from the Monstrous Menagerie except its maximum hit points are increased by the amount of damage you took creating it. You can only have one homunculus at a time.
At 14th level you can cause existing elements and compounds to come together in a complex, almost supernatural reaction. You may expend a hit die to replicate the effects of the fabricate spell.
At 18th level you accomplishes the ultimate feat of alchemy: the creation of a philosopher's stone. Using this stone allows you to do the following:
You may turn any amount of a less valuable metal into an equivalent amount of gold.
Once per year you may use your philosopher's stone to brew an elixir of youth, expending an additional 10,000 gp worth of materials when doing so and taking 8 hours. When a creature takes this elixir, they do not age during the next year, are immune to disease and magical aging, and that year does not count towards the creature's maximum lifespan. The first time they do so it also reduces them to their "prime physical age", mid twenties for a human or equivalent for other heritages. It may also be used as a reusable spell component that is not consumed for all resurrection spells, and a creature holding it may expend a hit die to replicate the revivify, raise dead, and resurrection spells each once per year, suffering the normal penalties from the spells if appropriate.