Marton Dhal was a wizard, and Gramling's former apprentice. He kidnapped Princess Mellisa and Susan Foreman with his winged apes. The wizard secretly conditioned their minds so they would do his bidding. The two women escaped from Dhal's fortress. While he was chasing them, his castle was destroyed by Earth Empire forces.
When he found them in Fluxford Castle, he planned to use them to operate Merlin's Helm, which Gramling had just put on. But he was surprised when Gramling, whose mind he thought he was controlling, switched bodies with him. Dhal was killed, since the Helm overloaded any human mind that wore it. (PROSE: The Sorcerer's Apprentice)