Potion of Diminution

Potion, minor, rare

When you drink this potion, you gain the “reduce” effect of the reduce spell for 1d4 hours (no concentration required). The red in the potion’s liquid continuously contracts to a tiny bead and then expands to color the clear liquid around it. Shaking the bottle fails to interrupt this process.

Source: Dungeon Master’s Guide p. 187. Available in the SRD