Smolderwing is an encounter inside the Onyxia's Lair set of Mercenary Bounties.
This bounty can be picked up from the Bounty Board and recommends a Party level of 30 to complete it.
You can unlock Smolderwing by first completing Kazakus, Golem Shaper.
Completing this Bounty will unlock the Dragonbone Golem Heroic Bounty.
Fire damage sets enemies On Fire. (Deal @ damage to themselves after they cast an ability)
Potential Smolderwing Bounty Rewards
In addition to earning Mercenary Coins based on your Party members, Bounties are assigned to specific Mercenaries to allow you to target loot better.
The following Mercenaries can have their loot appear in the Smolderwing Bounty: