Saponmancy

Numerous magicians have learned to use their alchemical knowledge to create soap and bathwater in the same way one would brew a magic potion.

These "Saponmancers" will often combine a variety of salts, soaps, perfumes, and powders to create concoctions that can bestow many possible effects for those who bathe in them.

Saponmancy can be a very lucrative, and secret college of magic. Well trained practitioners will often start their own bathhouses or spas and keep their recipes well hidden, for fear of competitors. Admittance to these businesses is often very expensive, and as such are mostly used by the wealthy and noble class.

Very rarely, these spas will become a visiting place for creatures from higher planes looking for a place of magical rest, very similar to the bathhouse in Hayao Miyazaki's "Spirited Away." These creatures could be anything from local spirits to angels or demons. Because even the Lord of the Nine Hells needs a break now and then.

Saponmancers are trained magic users and alchemists. As such, many are familiar with ways to use their powers in deadly ways. They are often skilled at creating explosives using the highly combustible fats and oils used in making soap, and many specialize in poisons that can affect entire water supplies and that are absorbed through the skin.

Some even delve into necromancy using grave wax, or the soap made from the fat of corpses for their bathes.

Gaining the effects of a Saponmancy bath usually takes at least 10 minutes of soaking as the ingredients used are diluted. The effects last 24 hours unless stated otherwise. Higher concentrations or certain catalysts allow the bather to absorb the effects more quickly and even instantaneously, but usually with harmful side effects.
 

Saponmancers use several specific ingredients for the water to achieve certain affects. Usually many other secret ingredients are required as well.

Here's some options for random Saponmancy baths or soaps

1- Blood Lily, gives the bather a d4 increase in Strength or a similar stat
2- Catnip, gives the bather a d4 increase in Dexterity or a similar stat
3- Ginkgo Biloba, gives the bather a d4 increase in Intelligence or a similar stat
4- Whitestripe Bamboo,  gives the bather a d4 increase in Constitution or a similar stat
5- Cherry Blossom Petals, gives the bather a d4 increase in Charisma or a similar stat
6- Vanda Orchid, gives the bather a d4 increase in Wisdom or a similar stat
7- Ginseng Root, gives the bather a faster reaction rate, any reflex save or something similar such as a roll to dodge will increase by d8.
8- Dong Quai, gives the bather an increased resistance to disease, any save against disease is at a plus d8, the bather can also save immediately on any disease they have already contracted. If this does not cure the disease it will not worsen for 24 hours.
9- Venus Fly Trap, the bather gains a "trap sense" within 15 feet of them. This is a general feeling of unease, but the player may not necessarily understand what the feeling is about. Rolls to find traps are at a plus 10.
10- Valerian Root, puts the bather in a deeply relaxed state but inattentive state, this acts as a sleep spell and lasts just as long. High concentrations last longer, even to the point of putting the bather in a coma.
11- Devil's Mint, puts the bather in a highly suggestive state, they will do what is commanded of them by anyone for the next hour. They get saves against anything they would not normally do. Skilled Saponmancers can even concoct a bath of Devil's Mint where the bather will only listen to them.
12- Crane Flower, gives the bather a general proficiency with "Eastern" weapons such as katanas, shurikens, nunchaku, bladed fans, sai, etc. If the bather already knows how to use these weapons they get a decent bonus.
13- Rue, the bather breaks out in painful blisters all over the exposed parts of the body, the bather loses roughly 10% of their health and can not gain it back until after 24 hours. This health cannot be recovered by any other way accept by Sopanmancy.
14- Aloe, the bather recovers all lost hitpoints
15- Sea Salt, the bather gains waterbreathing for d6 hours
16- Grave Wax from an individual, the bather gains memories as if they drank from a Goblet of Atli
17- Grave Wax from numerous individuals, if the bather is living this has no effect, if the bather is a corpse they rise as a zombie after an hour of total submergence.
18- White Lotus, the bather gains an aura of nobility for d4 hours, others will instantly recognize the bather as a member of some higher order or class depending on the local society, how they react is up to the individual
19- Grey Ooze Soap, the bather's flesh and bones melt away and they take on a semi-liquid state for d4-1 hours, while in this form they can not carry equipment and can generally only interact with the environment by making slam-like attacks. But, they can squeeze through the smallest cracks and take no penalty for doing so. When the user reforms they will be naked as they will have dropped all of their equipment.
20- Hydra Oil, the bather cannot be killed by decapitation for the next d4 hours. Instead when their head is cut off they will grow three new heads, these new heads will also be affected by the Hydra Oil bath. After the bath wears off, excess will shrivel away leaving the bather with a single head again.