From the moment Samiel got confirmation from the Akashic Records that he could obtain a Level Ability from assimilating the soul of the Transcendental inhabiting the body of the Forest Troll Chief, he couldn't really control his own greed.
He weighed his option before deciding on this one. Samiel, as a partial Eldritch Creature, was very sensitive to souls, and he sensed that the soul of the deceased Transcendental inhabiting the body of the Forest Troll Chief was on the verge of dissipation.
It was so weak that he could basically devour it without suffering any side effects, and this was a heavenly opportunity, as others of this kind might not come in the future once again.
He knew that the Transcendental inside the body of the Forest Troll Chief used most of his remaining power to force several evolutions in the body of the Forest Troll Chief so he could use him as a means to resurrect himself or rather to find a better and more powerful vessel.
