Selen Vinland is a character in Demon's Souls. She is the sister of Garl Vinland and only appears during Pure White World Tendency or Pure Black World Tendency.
5-2 Archstone, to the right of the first fog gate, on one of the tiny islands.
She tells the player that she is searching for her brother, Garl Vinland, to tell him the last words of their father. She asks if the player sees him that the player tell her. To complete her quest the player has to return to the location of Garl Vinland, after the defeat of Maiden Astrea, to fight his black phantom form, which has significantly more health. After defeating BP Garl he will drop the Crest of Vinland. Bring this to Selen and if you have 10+ faith she will give you the Ring of Devout Prayer, if not you will get some Darkmoon grass.
She says "I find something odd about this place. It brims with grime, but at once feels strangely pure." This could be her referencing the effect Maiden Astrea has on the valley.