Potion of Deceiving (5e Equipment)
From D&D Wiki
This potion is only used by those DM's that really want to mess with their players. This potion appears to a different potion of any type. The rarity is equal to that potions rarity. A taste test or use of magic to find out what kind of potion it is also reveals it to be that potion. However, this is not the case. Roll a D6, going in order for each effect, or choose one manually. Notes All effects can end whenever you want. Don't overuse this.
The effects of whatever potion this resembles are inverted. Examples: A potion of healing deals damage instead of healing, a potion of giant strength makes you lose strength instead of gain it, a potion of growth makes you shrink instead of growing, a potion of fire breath makes you shoot fire out of your behind or makes you breath ice, ect.
This effect is a bit custom. The drinker is rendered useless by some effect. Examples include: shrinking down to fine and being unable to use any their weaponry, having their bones vanish and becoming a puddle of skin and flesh, becoming to clumsy to do anything, becoming paralyzed, having time reverse on them to make them a baby an be useless, ect.
The potion is fake. It gives the drinker some ability, that doesn't work right, or just doesn't do anything. Examples: A potion of flight that gives them tiny butterfly wings that don't do anything, a potion of healing that makes them feel refreshed but nothing else, and potion of dragon form that makes them grow scales uselessly, a potion of diminution that instead causes their clothes to shrink, a potion of rat form that makes them become partially ratlike, ect.
The potion causes the drinker a disease related to the effect. Examples: a potion of fire breath that causes the drinker to erupt fire from openings on their body randomly dealing D4 fire damage to them and people around them, a potion of diminution that causes slow shrinking for D12 hours, a potion of anything that makes them vomit or leak human waste uncontrollably, ect.
Actually a different potion. Examples: a potion of healing that actually is a potion of sleep, a potion of growth that actually is a potion of petrification, a potion of polymorph that actually is a potion of genderswap, a potion of metal form that is actually a potion of sliminess, ect.
The potion is just defective in some way. Examples: a potion of diminution that causes random size change, a potion of fire breath with delayed activation, a potion of healing that makes you release gas that heals others not you, a potion of polymorph with extended duration, a potion of race change that slowly activates, ect.