Moghedien

Old Tongue for Spider, moghedien is a Forsaken freed by Ishamael at the end of season 2, who is portrayed by Laia Costa.
she has the ability to create near invisible assassins called Gray Men, is adept at the weave of Compulsion, and has a penchant for torture. despite being considered the weakest of the forsaken, the others fear her enough that they agree to team up against her. these fears are proven right when she murders the captured sammael at the end of season 3.