Inspired by the new Masters of the Universe Classics line.
The design is mainly based on the original box art, with some inspiration from the cartoon and the mini comics.
The structure of the castle is foam core.
The outside "skin" is Crayola Model Magic clay.
For the larger areas I used first built it up with Aluminum Foil.
UPDATE: I added some new elements to the bottom of the castle, I wanted it to match some of the comic book art.