Falsifal

The falsifal is a brown mushroom found in the forests. Its shape is curved and when you cut it, it releases a small harmless gas. But a talented herbalist who knows how to recover this gas will make a maceration with surprising effects on breathing.
A falsifal maceration doubles the value of the Constitution modifier (minimum +1) to calculate the time you can hold your breath and the number of rounds you can survive when you can't breathe.