This potion's container seems to hold fog that moves and pours like water.

At first glance, this potion vial appears to contain naught but thick fog. But as you observe closely, you see that the fog is actually a liquid, the fog but an optical illusion—or is it?

I Drink an Potion of Gaseous Form
The potion pours in smoky tendrils onto my tongue, light yet bitter. It desiccates my mouth, throat, and lungs to the point that breathing becomes difficult, painful. I become dizzy, stumble and spin on my feet, then—poof—I become vapor, my senses tingling as I occupy space in a strange, free-floating way.