A lamia is a weapon named after the creature of the same name. It is described as a spiky and particularly cruel whip, and is forbidden in most civilized countries. The weapon collapses into a small disk, making it easy to conceal. It was a favourite tool of the head of the Novigrad secret service, Chappelle.
In one of the opening scenes of Chapter I, when Geralt first meets Shani in the compound surrounding the Inn, she tells him that the Salamandra had beaten a child with a lamia. This serves to underline the extent of their evil.