Some "species" I came up with newly. Want to share so here it is -w-
"Diener", a rare found race which is meant to assist with the one they formed a bond with, a present the gods blessed the people with a long time ago. Dieners are always loyal and will never refuse their master's orders nor question them. Besides loyalty their personalities differ of course. They can only be identified by the aura they send off. Diener always has to be named by their master. When their master dies they lay away their name so a new master can bond with them, means Dieners are nameless when their Master passes away.
Dieners are immortal... Until they have found their ultimate Master. This one will offer a contract to this Master where they perform a ritual together. The Diener bonds themsleves to their Master for eternity, increasing their Master's lifespan yet also dying alongside them. The contract cannopt be taken back, even if Master or Diener want to or not. So the Diener always chooses their Master carefully to make sure they forge a bond with the right Master.