Unicron is a sentient metal sphere the size of a moon or small planet, that can transform into a giant robot. Depending on the contunity, Unicorn was: constructed by Primacron to scour the galaxy clean of live; a chaos god trapped inside a planetoid by Primus the good god; or a variety of other origins. But in all instances is very big, evil, and wants to destroy Cyberton, the Transformers, and the Autobots Matrix of Leadership/Creation Matrix.