From the Introduction:
Ego is a game that you play before you play your game. It is a Role Playing Game (RPG) that you play before, or rather as part of Character Generation for the RPG campaign you are about to start. At the end of an Ego session (or perhaps multiple sessions) you will have very unique character to play in your new campaign.
You are an intelligent item
In Ego the players take on the role of intelligent items. Intelligent items that have already been found by a group of characters. I'm sure everyone who has played a traditional RPG has run across an intelligent item at one time. They are usually amazing and very powerful magic gear that characters find. A big part of the magic item trope is that these items have a will of their own and will often exert that will and try to control a character.
Ego takes this trope and turns it upside down. In Ego, instead of playing a character who found an intelligent item, you are playing that item that has been found by a character.