The pale, red-headed wizard wears a blue robe with a purple mantle and cloak. After he changes, however, he takes the form of a cobalt-colored werewolf.
At first, the wizard will teleport around the room, typically opposite of the Master and either let fly with three skull projectiles, or a triple burst of lightning, aimed very closely. Sometimes, he'll cast lightning right after he shoots the skulls. The skull attack comes out very fast, so the Master will have to be quick on his feet to avoid damage. The lightning isn't a threat unless the Master is within striking range of his sword (but beware the small blast radius); naturally, this is the best time to attack the wizard.
Once the wizard has been damaged down to 50%, he'll undergo a transformation (during which he is invincible), revealing himself to be a werewolf! He's much faster in this form, able to cling to walls and body-slam the Master. At this point, it's simply a matter of attrition; the Master cannot hope to match the werewolf's speed for long and must dispatch him quickly. Due to the flooring, Magic Stardust isn't terribly effective here. The wolf will stalk the floor, causing medium damage if it touches the Master. If the Master takes to the platforms, the werewolf will wall-jump to attack. Rarely, the werewolf will howl and fire wolf-head projectiles from the wolf pillars that hold up the platforms.
An expert tip is to whittle the mage-form down to just above half, then deal a flurry of blows during the next opportunity; since the transformation, and the ensuing invincibility, doesn't begin until after the next teleportation, a furious set of strikes can reduce the HP that the werewolf will have. If quick enough, it's even possible to kill the wizard outright and skip the werewolf transformation entirely.