Vez is a unicorn-horned woman who is implied to be a member of, or at least closely affiliated with, the Wreath High Command.
She hires The Will to hunt down Marko and Alana, and tests the Freelancer by pitting him against a massive fire-breathing creature in her cave. Vez claims that a powerful set of tools called The Tablets of Prophecy have foretold Marko will be responsible for millions of innocent deaths.
When Lying Cat identifies this statement as a lie, Vez admits the capture is necessary in order to keep morale high and to prevent future possibilities for fraternization for the enemy. However, she also urges The Will to bring in any child they might have had "alive and unharmed," which suggests that she does not particularly desire the death of Marko, either (but her disgust at The Will's use of Language implies no such sympathy towards Alana).