Blood Seed & Shapeshifting
Life Drain!
Eren had managed to activate this ability at will after learning about it from Nina and his experience with the Domain of Wrath. He now only needed to shake his arm as if tremors ran through them while thinking about Life Drain in his mind to activate the ability.
He had come to realize that abilities would be bound to certain organs of one's choosing. Ranker's organs served as blank paper and higher consciousness as ink to etch runes that enabled one to wield abilities.
Eren had been wondering if abilities could get plundered if he has the ranker's organ that was etched with their ability. He may be able to assimilate that organ into himself through his half-blood powers.
Eren knew things wouldn't be as simple as he had made them out to be. Plus, ability wielders were a rare breed among rankers for him. So his experiments would have to wait.