Styrkaar is a Chaos Lord of Slaanesh created as part of the fluff surrounding the release of Warriors of Chaos during the early "Hordes of Chaos" approach and as part of the build up to the Storm of Chaos campaign. He is one of the Lieutenants of Archaon. Technically his model and that of his rival were existing generics given names and lore.
Born the son of his tribe's chieftain, Styrkaar was secretly guided from birth by a daemon named Sle'zuzu, who would appear to him, and only him, for as long as he maintained the secret of his existence. With Sle'zuzu whispering into his ear, Styrkaar knew all the right things to say to win people over, becoming more and more popular as he grew. He eventually toppled the former Jerg of the Sortsvinaer, his father Svengor, and merged with Sle'zuzu, becoming a Champion of Slaanesh. Gifted with a Daemonic Steed and eventually made one with Sle'zuzu as an an Exalted Daemon, he slew Archaon's former Slaaneshi lieutenant, Vandred the magnificent, and so took his place at the side of the Endbringer.
In End Times he was Sigvald's second in command (suprised Styrkaar did not kill him since Sigvald share the same "Magnificent" title as his former rival) where they went to attack Parravon. Unfortunately Abhorash was there and Styrkaar, lacking any plot armor, got his Slaaneshi pansy ass kicked in the balls/vagina.
Styrkaar is noteworthy as a canon transexual character; as a Daemon woman trapped in a man’s body he had to cut down a phallic symbol in the form of his predecessor in order to claim his title as fabulous leader, and sports the most famous hairstyle of gay/transexual icon Madonna (if made today, he would probably cover his armor in meat instead).
Although he did not completely return in Age Of Sigmar, a new kit of Warriors that includes female heads also included a head that is very blatantly Styrkaar, his horns and hair, although his facial expression is no longer mockingly jovial as he sports a nasty facial scar. Slaanesh may have saved him like Nurgle saved the Glottkin, but didn’t see fit to grant him the rank of Daemon Prince nor to fully heal him; interestingly, Slaanesh himself sports an unhealing facial scar from Khaine. Like father like son/daughter?