Gu Zhen Ren
His destiny to challenge the immortals.... have a feeling thay old venerable had a hand in reincarnating fy from earth the first time. The fact that a c grade was his life taight him about the gu worlds ****ed up laws, where the blessed gets everything and those unlucky mortals jist get ****ed over.
How can Fang Yuan choose to enslave someone unless Fang Yuan chooses to kill 1 less person than planned? The actual killing should not take any immortal essence (Remember the guy who killed 22 Gu Masters. People could kill more than expected. If killing were burning immortal essence, then killing a few more people would only slightly increase the risk of the plan.), so teleporting must be what is burning the essence. The enslavement cost a teleportation.