"Eureka" Phoenix Feathers that work the same as they usually do in solo content - autoraise. Put a cooldown of 180 minutes on them so that they can't be abused but do serve as a single chance per Eureka run (of 180 minutes) for a solo player to survive a knockout without the severe exp loss. It's all well & good relying on a friendly player to raise you but we all know that things happen.