Alright, here's a basic look at the main idea Shinsou and I have discussed. It won't be very fleshed out, but there's plenty of room for participation. Basically what we're doing is giving the calamity a cause, and a villain.

Prologue: Sixteen Aleraran assassins sailchute down over Corone by darkness, the last one killing the airship’s pilot as she goes. They land and perform a simultaneous spell using synchronized watches, causing the Lotho Mountain caldera to erupt, destroying Lornius, creating an earthquake and tsunami, and showering the land in ash, making it all but unliveable for anyone without the breathing apparatus they possess.

The main antagonist is an assassin named Vityr Sha'keth, whose older brothers Kron and Shynt were killed by Cronen years ago. In addition to causing the calamity, the assassins are acting the tip of the spear in an Aleraran invasion of Corone. Vityr has the additional goal of killing Cronen.

Shinsou and I have a main storyline planned which we'll be writing together, but there is room for plenty of associated side quests such as missions associated with some of the fifteen other assassins, or connected threads taking place in Alerar. If anyone is interested in doing a thread related to this I'm happy to help you come up with ideas for assassins, and will provide background information on the organization that trained them.

Until I talk to Shin about the details, that's pretty much all I can say for sure.