In the 1986 Masters of the Universe Annual one of the more unique stories is "Silvanos Threatened". Firstly we meet King Randor's cousin King Sullei, the hot-headed ruler of Silvanos. His sister appears later in the story; an elderly lady with an incredible inner-strength named the Prophetess. In the story it is revealed that the Prophetess is old friends with the Sorceress, and most strikingly of all, that she also knows that He-Man and Prince Adam are one and the same! Although this annual suffers, due to some odd-looking artwork throughout, this story is the book's saving grace.
(click on the image to see it at full-size)