CW: mainly the drugs, but mentions sex, kink and self-harm.
Turns out I need an Altered States sub-system for the Druid (BOSR/ Folk Horror/ Pagan/ Psychedelic/ Witch variant) I'm working on.
I'm sure there are some already out there, maybe already part of the setting or system you're using. Plus some links for drug-based rules resources.
My unadorned and undeveloped system is this:
- without shortcuts (and I mean drugs), it takes exploding d2, d3 or d6 hours to get yourself into an Altered State
- unless from drugs, it takes d2 to d6 turns to come out of an Altered State; these dice might be exploding if it's a particularly powerful Altered State; what you have to do depends on the Altered State
- in an Altered State, you are -1, -3 or -6 on all Ability Scores depending on how deep you go; penalties may persist afterwards, from fatigue, injury or sickness
- while in an Altered State, give your character sheet to your GM - you may not consult it, take notes or keep written records during this time*
- if you need a dice roll for going in and coming out, I suggest our old friend 2d6 vs. 7, 9 or 11; ability and skill checks would also suffice
The basic idea is that the Altered State, while it has other uses, should carry a penalty of some kind - under the right circumstances, this could just be the time required to achieve, utilise and emerge from it, but I'd consider making the handing over of the character sheet an absolute.
Ways to get into an Altered State: dancing, chanting, drumming, breathing techniques, meditation, humiliation, sensory deprivation, fasting, over-indulgence, heat, cold, suspension, submersion, asphyxia, tickling, flagellation, sustained vigorous exercise, spanking, masturbation, near death experience, sex, wrestling, fighting, staying awake, prayer, staring at something, crucifixion, fever, disease, concentrating really hard, madness, fear, laughter, frenzy, sadism, pain, flickering lights, acting really convincingly, silence, screaming, singing, counting, extreme mathematics, hanging nine days on the World Ash with a spear in your side, a really long walk.
...whether magickal herbs or magic mushrooms.
There are some rather bland rules for Intoxication in the 1e AD&D DMG, which could be expanded to cover all Altered States if you prefer the system.
Carcosa has its Desert Lotus varieties, with their own defined effects and durations.. Blue, Green and Jale would be the obvious choices, with White Lotus a borderline case (you become a mindless zombie). Black Lotus is fatal, but so are some poisons that have medical uses in small doses.
For drugs (entheogens) as an integral part of the setting/system, you should look to the excellent aloneinthelabyrinth.blogspot.com and check out Pariah - a proto-neolithic psychedelic animist rpg.
Pariah has flavourful rules for ritual (and recreational, I suppose) use of entheogens, with one of the explicit purposes being travel to other worlds (which are also delicious). They are not just 'magic potions' - they're a session in themself.
Applied to another setting, you might decide to leave out the cosmological aspect - maybe the drugs just aren't as good as they were at the dawn of time, or make them incredibly rare, or set up gatekeepers, or have the common supply be so over-processed that only prodigious consumption (or in its natural/pure form) would have any special effects.
The Ten Foot Polemic system gave me the idea for handing over your character sheet when in an Altered State, as taking Alterket means you no longer keep track of your hit points, the GM does.
And Goblin Punch has a selection of drugs (including for Dragons) you can choose to tone down for the family audience. Or not.
Just as mechanical and narrative effects of drugs can be used to represent a non-drug Altered State, so can rules for Tolerance (you need more chanting to get in the mood) and Addiction (you won't leave the meditation centre).
The Ghastly Affair system includes some fairly comprehensive mechanical/narrative details on IRL drugs of the Gothic/Ghastly Age - laudanum, hashish, peyote buttons etc. - though they do include some supernatural side-effects, including being Attractive to Fairies and increasing the effects of Divination.
*there may be individual IRL circumstances where this isn't appropriate - issues of communication, memory and trust, for instance.