Night is right. They've turned the Thief into Bin Laden. When a Thief levels up, so does the Mage. And what prevents the Mage from buying a Thief hero in an independent tavern? There are many nuances here.
And let's start with the nuance that indicates that by the time the Mage finds a tavern (if there is one, although when playing as: Barbarians, Nature, or Necropolis, he can buy one in his own castle! :D), the Thief will have already leveled up quite a bit! :D And it will be more difficult to catch him then! :D :cool: