Tang Zhen was fair in his work. Since he was using someone else's body, he would definitely help that person fulfill their wish.
Otherwise, if the soul and body were not compatible, with remnant thoughts causing trouble in the body, it would make it easier for him to be exposed.
Then, he would use the identity of an ordinary person to secretly investigate the traces of the enemy and find his relatives from a different world.
The world was peaceful now, which meant that the enemy had not taken any extreme actions.
Unless there was no other choice, the enemy would not destroy the world. That would only increase the difficulty of the mission.
When given a choice, the enemy would use a more secure method to achieve their goal with the least cost.
After the enemy collected the refined blood, they would gradually possess Tang Zhen's ability and sense it through their bloodline.