Sadly, I'd actually be inclined to say if you do not help, your fate will be more likely to be decided by an outside force. We're not sure what the enemy is as yet. But, we know we need your help to stop it. And whatever it is doing, will affect every world, every reality and every time. There will be no escaping it.
However, while here, you are in no way forced to help fight. Just asked to contribute to the running of the town. To earn your keep as it were.