Una Persson is tall, with a slim "boyish" figure, with dark hair cut short in a pageboy haircut (but not always). She often wears military garb.
Oona von BekEdit
Oonagh von Bek, the adopted grandaughter of Oona and Ulric von Bek, stated:
"I know most of it's true, because I heard the parts I didn't experience myself from Una Persson, as she calls herself now, that mysterious adventuress who spends so much of her time in eastern Europe and never seems to age." -The White Wolf's Son
This suggests that Una Persson may in fact be Oona the Dream Theif's Daughter in disguise.