The Sorceress of Castle Grayskull endowed Prince Adam with the power to transform into He-Man, which he did by raising his Power Sword and proclaiming, 'By the power of Grayskull.' Once the transformation was complete, he would continue, '.I have the power!' The differences between Prince Adam and He-Man were minimal He-Man had a slightly deeper voice, a different wardrobe, and slightly darker skin and hair.
