The potion's yellow fluid is streaked with black and swirls on its own.

After the effect is finished, the caster is Stunned for 1 round.

This potion bottle is swaddled in layers of soft cloth, and no wonder—due to the yellow and black liquid within constantly swirling and sloshing under its own power, the bottle would eventually crack due to the vibrations thrumming through the glass vessel.

I Drink an Potion of Speed
I unstopper the bottle and smell a strong scent of licorice wafting out. I bring it to my mouth and drink the swirling potion, feeling it swish around in bright spirals before I manage to swallow it. This fast-churning magic sends an invigorating hum of energy throughout my body, and I feel as impossibly quick as a hummingbird’s wings.