Zarakynel, the Bringer of Torments is the best and (apparently) most beautiful of Slaanesh's creations, but his/her/its model is a six-titted mmonstrosity that looks like Shiva had a baby with a daemonette and an albino. He/she/they/them has fun raping Eldar, especially the exodites, and her favourite delicacy is spirit stones. She is well known as the bringer of torments, the soul-eater, the unholy one, and fucking ugly. She quadruple-wields swords and is a complete rape monster. Literally.
At one point, she had a run in with Iskandar Khayon, taking the life of his bitch Nefertari. Before he/she/it could take Nefertari's soul, Khayon used his psychic powers to blast her into the warp. Even though she survived the encounter, it was more than a millennium before she could regain corporeal form. He/she/it vowed to fuck up the goddamn space pansy. One of her most notable appearances is on a planet called Sherilax. A bunch of pleasure cults were having a violent uprise against the planetary governor. The pleasure cults were pleasing Slaanesh greatly, so he/she/it/Hermaphodite/who the fuck even knows sent Zarakynel who then appeared and converted the Entire planet. It was, in fact, so horrid that even the Inquisition refused to write what really happened there. Oh God.
On the TT
She is an unholy rape monster (literally), dropping to just 450 points in the new edition rather than the previous 666, and is still a Lord of War. She has a 14" move at full wounds.
Her first weapon, the Souleater blade, is S+2 for 6 attacks at s9 AP-4 D3, but to wound rolls of a 4+ deal 3 mortal wounds instead. Like regular Keepers she has 4 additional attacks, her slicing claws are S7 AP-4 D3. Like all Slaanesh daemons, she fights first even if she didn't charge.
To get her into combat Shalaxi has 4++ and can cast 2 powers (she can also deny 2 powers). Zarakynel has gained ability to regain d6 wounds if she killed a model in combat. From the recent forgeworld book she hasn't turned out too badly.