Lady Wembik was a Valdigian whose son, along with Lady Mesca's was part of a succession crisis on Safeplace. She refused Mesca's son to become the next king to such a degree, that, under the guidance of Zara, poisoned Mesca.
She tortured Amy, whom she blamed for the poisoning of Lady Mesca. She was surprised that Amy did not respond to the torture apart from a slight bruise. She was injured in the Ice Warrior attack and had to get her wings removed. Amy negotiated with Lady Wembik and Mesca, and they agreed the solution was to marry one another, meaning no matter whose son became king, he would also be the son of the other one. She was trapped inside the castle on Safeplace, which was a segment to the Key to Time, once Zara turned it back into its original form, and released once Amy briefly turned the segment back into a castle, allowing her to escape before the segment was turned back into a crystal. (AUDIO: The Judgement of Isskar)