Potion of Maximum Power

From Explorer's Guide to Wildemount, page 268.

Description
Potion, rare.

The first time you cast a damage-dealing spell of 4th level or lower within 1 minute after drinking the potion, instead of rolling dice to determine the damage dealt, you can instead use the highest number possible for each die.

This glowing purple liquid smells of sugar and plum, but it has a muddy taste.