Undine (ウンディーネ, Undīne) is Claymore #11 and is notably brash and aggressive. Unlike other Claymores, she carries two swords, which gives her the title Undine of the Twin Swords (双剣のウンディーネ, sōken no Undīne). Undine appears as a bulky, muscular woman, however this is a result of shapeshifting. Her natural form is small and delicate. Deneve deduced that as a young Claymore, a friend died protecting her and out of shame she developed the attitude and build she later possesses. One of the swords she carries belonged to the Claymore who died protecting her. Probably because of this experience, she bullies her weaker comrades and tells them to leave the battle but only because she worries for their safety.
Undine is one of the division captains in the Northern campaign and led Deneve (#15), Zelda (#24), Claudia (#36), and Juliana (#43).
She was one of the four captains killed by Rigardo during the second battle. Deneve used Undine's "borrowed" sword as her commander's gravestone, and she also took Undine's own sword in memory of her comrade and captain.