Welcome to Weavefall!
This westmarches style campaign will revolve around that cataclysmic event known as weavefall. Weavefall refers to an event where all creatures connected to the weave (all arcana magical creatures) suddenly died instantaneously. Beyond this large ravines of untamed magic known as weavines formed cutting the world into sections. The only safe haven is Greyhaven where the clerics of Tyr welcomed all refugees.
Weavefall occurred 50 years ago since then Greyhaven has grown to an unsteady peace between many different clergies, druid circles, and non magical guilds. Expeditions are sent out regularly to map and look for new places to settle the unforgiving lands. Your character is an adventurer interested in joining the expeditions.
Good luck!