White Fang is one of nine optional trophy quests. It is obtained by killing a large wolf, Voref, which the Royal huntsman mentions is roaming the swamp forest. Only one trophy quest, The Beast of the Sewers, is not optional, making a total of ten. (Note that if you have this and Predatory Wvyern active, you can only take ONE trophy at a time, so make sure not to kill both bosses unless you can remember where you kill the second one, as once dead, these bosses do NOT respawn)
You will find the wolf roaming the swamp. It only spawns after dusk and before dawn, and will not appear when you are doing the quest to save the brickmakers. Kill it and take the trophy off from its dead body. Take the trophy to the Royal huntsman in the Trade Quarter for a nice reward.
I killed the great wolf. He shall hunt people no more. I should deliver the proof to the Royal Huntsman and claim my reward. I need to give the trophy to the Royal Huntsman and claim my reward.