While we've already posted this week's episode preview for Friday's all-new episode of The Clone Wars, it should be noted that SW.com has added the preview version of the episode guide for "Monster" (S3 Ep. 13) with the following synopsis:
"When Count Dooku calls upon the Nightsisters seeking a replacement for Ventress, she and her kin seize the opportunity to exact revenge. Ventress visits the far side of Dathomir and the males of the planet seeking the most brutal and powerful warrior among them. Through their witchcraft, the Nightsisters transform Savage Opress into a monstrous killer designed to turn on his new master."
As per usual, we'll be sure to update this post when the full version of the guide goes online.