If you totally destroy a container by forcing it with a blunt weapon, and one or more potions shatter as a result, they should cause vapor effects around the chest’s area (which will always affect you, of course).
If a potionless conduct is implemented, this should break the conduct.
It should be possible to build up a resistance to a potion by drinking or inhaling fumes from it too frequently, making it work less effectively on you or not at all. This goes for both negative potions, which is good because monsters can’t use them as effectively against you, but also positive ones, which is bad because you will stop getting as much benefit out of them.
Replace the wand of teleportation with a potion of teleportation (leave the ring and scroll, and possibly the spell of teleport away, as-is). You could still teleport monsters, but possibly not objects any more, by throwing the potion of teleportation which would then randomly teleport everything that it gets on or which breathes its vapors.
This also is intended to make the Astral Plane more difficult by removing easy zaps and snaps of the wand, making it a much more limited resource.
Throwing “attack” potions (sleep, paralysis, blindness, etc) should either always hit the target, or hit the floor at the target’s feet (causing vapor effects) if it fails the to-hit roll.
Strangulation protects you from drowning, since you cannot inhale water if you can’t inhale at all. It also prevents potion vapor inhalation effects and the inhalation effects of gas clouds. Basically it works like magical breathing except you die in 6 turns.
Allow sinks to be catalysts for alchemizing things. (Or possibly add a “cauldron” as a new piece of dungeon furniture, but that’s iffier.)
Inhaling vapors from a potion of gain level produces a message like “You smell hard work” or “You smell elbow grease” (perhaps if hallucinating), granting you 10% of the experience points needed to advance to the next level. Monsters may be similarly affected.
Note that the 10% is calculated just based on the level thresholds and your own experience points don’t matter (only your current level). If you are level 5, with level 5 reached at 120 points and level 6 reached at 200 points, you will always get 10% of (200-120) = 8 points.
Remove restore ability vapors healing monsters to max HP, because that makes no sense.
There should be three ways to interact with potions: drinking them, getting them splashed on the exterior of your body (e.g. having them thrown at you and hit you), and inhaling their vapors. These should all be fully symmetric between the player and monsters and have noticeable effects for most if not all potions.
The key missing one to implement is the “topical” potion effects. Currently, the only potion with topical effects is acid, and thrown potions only do vapor effects to the monster they hit, which is often weak and ineffective. Topical effects would probably be best implemented as working the same as quaffing the potion, or a bit weaker. This would also be useful for buffing potions that monsters throw at the hero: the vapor effects of, say, a potion of blindness are so short that it doesn’t make much sense for the monster to throw it rather than doing something else, but if blindness splashing in your eyes causes a significantly longer duration, it makes more sense.
You can dip a potion into a sink to pour water into it from the tap, diluting it and causing runoff which subjects you to vapor effects (hopefully identifying it). For simplicity, the 1/30 chance of a random potion coming out of the sink should probably be ignored here.
Alchemic golem, which is basically made out of potions. Its melee attacks expose you to random potion or potion vapor effects. Killing it drops a few random potions and causes more random vapor effects. It can spontaneously explode when it hits something, with a greater chance when you hit it in melee. The explosion obviously also causes multiple random vapor effects to the area, and scatters potions around (by throwing them, so they tend to smash if they hit anything).
When potions break on the ground, they leave puddles of that potion. Pets can drink this puddle to get the effects. They also give effects (vapor effects, plus acid burning) to any monster standing in them, which is nice because it makes it harder for the player to stand in one place and fight a horde of enemies. Not defined what should happen if multiple potions mix in one spot - alchemize perhaps.
Vapors from the potion of polymorph should cause a brief or minor polymorph. Possibly the “you feel like a new foo” effect.
Polymorph potions affect all monsters adjacent to where they shatter.
Make more potions effective for throwing at monsters, first by making the vapor effects hit more than just whoever they were thrown at (i.e. splash effects), and then by making more potions have a vapor effect that affects monsters.
