Swarm
The experiments he wanted to do with the elder were related to his Dream Domain, he was planning to create nightmares inside the Domain and make it as realistic as possible.
Jayden started with the one in which he saw countless mosquito like creatures, even after many attempts he couldn't get the desired effect, he wanted to make it appear as a complete reality, then he would be able to use it in many ways and it will have vast usage in battles.
Just when he was getting closer to the final product third elder died, therefore Jayden had to stop the experiments, then he sent the head of the third elder to the king's room placing it at the centre of his bed while he sent the rest of the body to Qiang's room, laying it beside the sleeping Qiang.