Serena Bloodfeather is an encounter inside the The Barrens set of Mercenary Bounties.
This bounty can be picked up from the Bounty Board and recommends a Party level of 7 to complete it.
You can unlock Serena Bloodfeather by first completing Air Elemental.
Completing this Bounty will unlock the Apothecary Helbrim Bounty.
Potential Serena Bloodfeather 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 Serena Bloodfeather Bounty: