Your character is, well, a character. He or she is controlled by an outside force. Everything that character will do is already determined by this outside force; they just don't know that.
One day your character ends up in a strange land with no idea where they are, and suddenly they are in control of their future. The little voice in their head telling them what to do is gone, and they are the masters of their own fate. It's quite an odd feeling.
It would be very fun except for the fact that they're very far away from home.
So, with their new decision making skills and summoning abilities, the characters start to head home. Their thoughts become realities; if they can imagine it, it exists. This has a few negativities, of course, but I'll explain that in the rules.
They can't just wish themselves home, either. They must plane jump to get home, and that's where the fun comes in.
Be careful what you wish for, little charrie...
A bunch of inter-parallel-universal dweebs have been thrown together by an odd outside force and now their very thoughts will decide their fates.