When you drink this potion, you gain the "reduce" effect of the Reduce Target.

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.

I Drink an Potion of Diminution
I watch the faint pink color of this magical concoction contract into a tiny cherry-red bead—then flood back out—a high-pitched whistle emitting each time it shrinks. I drink it and feel my tongue and throat perform the same, odd contraction. I sigh, my voice high and squeaky like a mouse. The potion settles in my stomach after a few heartbeat-like sensations, a process during which I see the world around me enlarge considerably.