A banshee, also called a beann'shie, is a female spirit who cries on Saovine night, wailing a warning of those who will die. Banshees are not specifically malicious spirits, though meeting one is considered to be an omen of the worst kind.
Their appearance varies, though most often they're pale, thin women wearing grey vestments, with burning red eyes.
Beann'shies howl and shriek, and if you hear their cry, you can know you'll join the ranks of the dead that night. – beggar from Dun Dâre
Old gossips claim beann'shies are the spirits of women stuck between life and death due to traumatic experiences. Their wails and howls are considered ill omens of imminent, inevitable death, though they are said not to attack the living themselves. Most often they appear in the form of pale, tear-streaked women with shriveled faces and wrinkled, corpse-like bodies.
They fight in a similar fashion to other specters, however Yrden is no longer necessary to force them into corporeal form nor do they disappear and summon friendly wraiths to stall for time.
They have new abilities which differentiate them from their fellows. One is the infamous scream which will stun and disorient Geralt if he's caught in its wake, opening him up to melee attacks.
Another new attack is to summon friendly skeletons to mob Geralt and restrict his freedom of movement. These are easy to dispatch, the beann'shie will not heal itself when the skeletons are active.
Safest way to kill the beann'shie is to sidestep its claw attacks and retaliate with quick strikes laced with specter oil. Use Quen to mitigate damage whenever possible and try to get rid of the skeleton nuisances with area-of-effect attacks striking this spectre at the same time.