Anti-matter, reverses the effect of the Reagent.
Poison? Antidote, makes the player resistant to Poison.
Gale? Stability, Temporarily prevents a player from being knocked around.
now, what about potion effects like Water breathing, Shark Repel, Love, Luck, or Agility?
For potions that have opposites, they change to their counterpart: Agility → Slowness; Clear-sight → blindness; Warding → Insanity; Healing → Harming; Revealing → Invisibility. Naturally working the other way.
As for the rest, we can be funny with them, maybe as a way to obtain this Anti-matter catalyst:
Suffocation
Water breathing turns into Suffocation, which reduces air capacity. Stashes of Anti-Matter could be found in some underwater structures that emit a Suffocation aura.
Shark Bait
Same for Shark Repel, which turns into Bait, luring even more sharks than blood. underwater structures that will be hounded by sharks should somebody swim into them.
Misfortune
Luck turns into Misfortune; Which reduces all luck (Aura V Misfortune potions
). In this case, i guess a fortress that constantly spawns enemies and requires a person to collect 3 of their drops to get a bunch of Anti-matter.
Hatred
Love turns into Hatred; when applied to others, it makes you only capable of damaging the person/thing that applied it. When applied yourself, prevents you from getting this status. Hatred would counter love, having both will cancel eachother. Imagine a room with a mini-boss, that will spawn a minion that applies Hatred.
Weakness
Power turns into Weakness, which obviously lower damage. Maybe a dungeon that you have to deal a certain amount of damage in time to recieve rewards.
Fragility
Iron-skin turns into Fragility, which increases all damage you take, although it also increases speed. Imagine a chamber that constantly barrages traps that you have to run through without dying.
Drain
Energy-Regen turns into Drain, which constantly lowers energy. applied in chambers that only stay open based on how much energy you have, the longer you stay with higher energy, the deeper you can go for more rewards.
Fog
As for Smoke, it turns into Fog; which allows you to only see nearby yourself (like the ingame variant). I cant imagine much of a chamber for this, except for a maze or something. If this were a high quality poton, it applies fog to the whole map like (like the opposite of clear-sight removing fog)
I imagine all these would be drinkable, but can be put back into a pot as a reagent to transform it into another potion type or something. And just to say, a Tier-V Anti-Potion would be negatively as effective as its positive counterpart: Misfortune-V reduces Luck by the ammount Luck-V increases it.
Obviously, Interchange and Elysium are exceptions, because they always brew into their respective bottle. But imagine getting Permanence and Tartarus Potions lol.
Mystery Potions will immediately apply every negative status