Return the Burning Gem and 15 Infused Burning Gems to Maurin Bonesplitter in Desolace.
Death is most desirable for those despicable creatures that turn their back on their liege for such selfish reasons. But death is not enough when dealing with those that have given themselves over to the darkness.
Take this gem. When one of the Burning Blade's near death, activate its magic. The spell shall pull the corrupted spirit out of its victim, leaving an infused gem behind.
Bring me these infused gems so I may dispose of them properly.
Go now, and may you elude death.