Unless our characters are going to be demigods or epic tier adventurers restoring peace to an entire world seems a bit beyond us. World peace is pie in the sky idealism even in the real world, in a world where there are Undead and Demons tearing around it's an even less practical goal. But the pursuit of -a- peace is a good starting point. What if instead of us just being disconnected people we're all tied to a single event within Termina, a peace summit between two great powers, a last effort to resolve their differences before the outbreak of a full-scale war that would result in both sides suffering terribly and Termina being crushed in the middle, inevitably annihilated or conquered?

Obviously the peace summit goes tits up like a Brazzer's production, probably due to the influence or direct attack by a third party.