Brine Potion

Brine Potion grants the user immunity to psionics (such as Illithid's blast) for 1 turn.

Baldur's Gate II: Shadows of Amn

 * Underdark - Mind Flayer Dungeon - 8 potions can be gained in the birthing pods

In-game description
"A potion obtained from a briny pool in which young illithids, tadpole like creatures, live and grow. When, used, the potion will temporarily make the user immune to psionics."