Terpsichore

Also known as the Dancer at Dusk. This enigmatic being never says a word. Instead, she is always dancing. Her form shrouded by veils that shift like shadows, she drifts through the Palace of Shimmering Waters like a ghost. Her primary aspect seems to be grief; being in her presence can bring the strongest mortal to tears of sorrow.

Ostensibly a fey of the Winter Court (specifically Morrigan's court), although that fact is disputed by some. Her true nature is unknown.

It is said (and attested by Fiona ka'Anu of Half Measures) that dancing with her, under the right circumstances, brings healing from grief--that the veils are formed from the physicalized remains of pain and sorrow experienced by others that the Dancer takes upon herself. Doing so is not easy, however, especially as many are attached to their grief.

Has a "daughter" (how that is even possible is part of the dispute as to her nature), Sorrow's Thorn. Very disparate characters.