Captain Aresin is an officer of the king's guard. He resides in Daggerfall, Glenumbra. He can be found north of the Daggerfall Castle. He appears to be in charge of the protection of the king, and it is with the him the Vestige corresponds during the Blood and the Crescent Moon questline.
Guards will comment about a dog, which, if interacted with, will lead the Vestige to the dog's former owner's deceased body. This quest involves speaking to three merchants, listed on the Daggerfall Market Shopping List, in order to solve the mystery.
Bloodthorn assassins plan to kill King Casimir. If the king dies, the entire Daggerfall Covenant could fall apart.