Prince AU:  Arxus lives in the town bordering the castle. He works as a black smith and is very good at it. Leaning from a young age to help his mother who raised him and his sister all alone.

Turns out his unknown father was actually one of the princes. And when the princes only (legitimate) son dies, Arxus is found and brought to the castle. As a commoner who suddenly finds himself inside the castle walls he has a lot to get used to, most of all the extravagance and the wastefulness he quickly notice. 

He tries to fit in, especially when under the watchful eye of his father the prince and grandfather the king. But one does not simply go from a blacksmith in town to a royal prince without mishap and struggles.

 Apocalypse AU:  The world has ended and Arxus had found and joined a community where he resides. It's not that big of a group and they all share everything. Food, water, loot. Anything. They have working farms on site and everyone pitch in to do different jobs. Arxus is an ex-military and therefore usually just sticks to training children when they get old enough to wield weapons.