The Phosphorescent Liquor is a strangely luminescent drink offered by Prince Vivescu through his thugs in Cartouche’s tavern in Uchronic Paris. It was used in an attempt to poison Claude. It nearly “knocked him down”; a strong will can resist it.
Its nature is unclear: a magical potion, a poison, or an extraplanar substance. Its origin is unknown, possibly linked to “the Serpent.”