White Gull

White Gull is a potion that can serve as a hallucinogenic beverage or as a substitute pemids
 * The duration of the effect is only long lasting if the potions is consumed as a hallucinogenic beverage.
 * The toxicity of White Gull is medium but only when consumed as a hallucinogenic beverage. When used as a base, the toxicity is irrelevant, only the resulting toxicity of the brewed potion counts.

Source

 * Lambert, during the A Potion for Triss quest in the Prologue.
 * The Book of the Swallow

White gull is required to brew a number of top-tier potion upgrades and complex alchemy reagents: Bílý racek Weiße Möwe Gaviota Blanca Mouette Immaculée Gabbiano bianco Fehér Sirály Eliksir Biała Mewa Белая чайка