He's the embodiment of what a Kamen Rider is - a tool of evil that grows into a force of good, though there are times when they slip back. though in Tsukasa's case it's more of a 'well I didn't get enough sugar today so let's destroy a world' slipping back. He just is a chaotic force really.

Actually he absorbs the potential energy so he can eat it just not in a way that he can enjoy with tasting and feeling.