Aerin is an Imperial residing in Riften. He rescued Mjoll the Lioness from outside the Dwemer ruins of Mzinchaleft and nursed her back to health. He spends most of his time following her around. He frequently expresses the desire to travel outside Riften, to see if things are as bad everywhere as they are in Riften.

Should the player marry Mjoll, Aerin comes with her when moving in with the player.

If Mjoll is inducted into the Blades, Aerin will eventually relocate to Sky Haven temple. He still talks about "this city" and continues to use his standard Riften-base dialog.