Sven Advensen was a retired Imperial Soldier and Count of Darkmoor estate. He had a wife, Lady Inga, and a son, Jonni. He was a distant relative to previous Darkmoor Keep inhabitants and had little to none royal blood.

Sven and his wife were the final caretakers of Barenziah. They raised her as their own daughter, tutored her and allowed her to train her archery skills, until she ran away from their care at the age of 16. There are conflicting accounts as to her reasons for the escape.

He is mentioned in the The Real Barenziah, Book I, and Biography of Barenziah, v 1.