The stats on this bow differ between pc and ps3/xbox360.
pc Despite its description, it works on Animals as well as Beasts. Against its preferred enemy type it is one of the best ranged weapons. Combined with Scattershot it is useful versus deepstalkers in the Deep Roads, especially on higher difficulties.
The following characters, lore and events are non-canon in Dragon Age and exist only within the Dragon Age tabletop RPG.
In the Dragon Age (tabletop RPG), Wolf-Killer is available as a "permanent magic item" reward for player characters. The longbow is one of the most powerful weapons available in the game.
“The story of this ironbark longbow’s creation has been lost. Though it appears not to have been crafted by a mage’s hand and no trace of lyrium can be detected within it, it has the uncanny habit of sending its shafts through the hearts of the beasts it is used to hunt.”