Welcome! I hope you enjoy your stay.
On the topic of your writing, as CAL-9 said, you could do something of your own design, but within the framework which has already been established. Personally something about a Lightless Guardian fleeing the City when the Red Legion hit, could be emotionally gripping. Trying to survive in the wilds outside the City, encountering possible resistance movements, and attempting to avoid Red Legion pursuers.
I guess the ‘best’ lore to wright about is what you’re most interested in. At the end of the day if you don’t care about what you’re writing, it wont the the best it could be.