The Banshee With But One Nostril (or simply "The Banshee") is a cryptic beast that had been haunting the Highland Quid Clan until Gordon showed up. These creatures are actually Seal Women put under The Curse of the Banshee.
When The Banshee rises up out of the swamp, she comes looking for a sacrifice, and will go anywhere to get it. She has a spine-chilling hiss that can be heard across the land, and tentacle nails that could constrict you until your eyeballs bug out.
This creature had been haunting the Highland Quid Clan for years, while the clan catapulted sheep her way to keep her satisfied. When she hears The Song of the Sea, the beast turns to stone, then the stone breaks open to reveal a Seal Woman.