Dargon, Traitorous Cur, is a Unique Brigand found in the Highlands Passage in Act I of Diablo III. He only spaws for the A Reputation Restored event.
In combat, he has no affixes, but when he sees the player, he will flee, seeking help of a nearby Champion Dark Berserker group. Killing him is required to end the event and win Kyr the Weaponsmith's favor.