The beast dropped out of the portal and landed with a thunderous crash on the street below, shattering the glass in every window within fifty feet, including the one in front of Ahven. The hunter smiled as he pulled the mask over his nose and mouth, then began sprinting toward the building's edge. When he reached it, a single powerful leap would carry him far out over the street to land squarely on the Demon's outstretched left arm, and from there he would reach the monster's back in two quick strides, each step taking him farther than most humans could jump with a running start. 

Once on the demon's back, he would anchor himself in place, ignoring the (presumable) impact of the large metal thing that had fallen, or perhaps been thrown, on the shoulder next to him. With any luck, the demon hadn't noticed his presence yet, and wouldn't until he made himself known via some offensive manner.