Potion of (temporary) Godly Power (5e Equipment)
From D&D Wiki
Gives the user powerful abilities for a short period of time, and then they backfire.
Depending on the rarity, the user gains a certain number of effects for a certain amount of time. You choose the effects. When the time ends, the user has the end effects of all of his effects activate, and the other effect deactivates. The end effect ends after a long rest or when otherwise stated.
Uncommon: 1 effect, lasting D4 minutes.
Rare: 2-3 effects, lasting D6 minutes.
Very Rare: 3-5 effects, lasting D8 minutes.
Legendary: 4-7 effects, lasting D10 minutes OR 1 effect, lasting D20 minutes, with no end effect (the other effect ends still).
Growth: The target grows D4 size levels, not including gear (gear breaks). They gain 2 strength increase per level, which can go above 20, and -1 Dex per level which can’t go below 0. Walking speed is multiplied by 1.5 for each level. End effect: After returning to normal, the target shrinks the same amount of levels they grew. Invert all effects (-2 str, +1 dex, half walking speed).
Power: Roll a D6. 1= STR. 2= DEX. 3= CON. 4= INT. 5= WIS. 6= CHA. The stat increases by D8, and can go above 20. End effect: the target has the boost inverted, after they return to normal. This can’t go below 0.
Ghostly form: The target gains a certain ability. If they wish to, they can move their body through any surface. They can take a reaction (recharge 4-6) to avoid an enemy attack. End effect: all of the targets clothing and gear fall through them. The target now cannot interact with anything, and cannot be harmed without magic.
Shapeshifter: The target can now cast polymorph without components or spell slots as a bonus action. Normal rules still apply to polymorph. End effect: the target begins to transform uncontrollably. Every turn, they must succeed on a DC 15 Con save or be polymorphed into a random creature. With this polymorph, there clothing falls to the floor (they don’t decide).
Miasma: The target can now use there action to create a powerful sickening miasma around them. Anyone within a 10ft radius is affected. They all must make DC 18 Con saves or become revoltingly sick. For each of them, they descend into a fit of coughs, a series of spasms, a large vomiting session, a horrible loss of bowel control, a choking fit, a short session of bleeding from all openings, or any other disgusting sickness. This takes their turn. End effect: this miasma comes into play, consuming your action every round. This time, it also affects you.
Body transformation: The target gains a random transformative effect. You can choose, but it has to be good and affect gameplay. Some ideas are giving them hard scales that improve AC, giving them spines and a spiny tail that can deal damage, growing sharp claws, growing wings, gaining powerful eyesight, or such. End effect: the ability swaps over to weaken them. Hard scales can transform to incredibly delicate membrane, wings can become leg loss, claws can become hand loss, you get it.
Spell power: The target gains a complete refill to spell slots, and they also gain D6 extra of whatever there second best level is. They can also use any of a sorcerers meta magic abilities for free in there spells. End effect: the target suddenly loses all of their spell slots in a blinding flash.
Come up with your own effects, I didn’t make nearly enough.