Chaos Everywhere
Just after Jake disappeared underground, a huge BOOM shook the earth, the resulting jolts nearly causing him to lose control of his Aether. The epicenter was exactly where he had been a mere second ago. If that had happened, the hundreds of tons of rock around him would have buried him in an instant.
His body was strong enough to withstand that kind of pressure, like a block of metal could support the weight of a mountain without necessarily breaking, but it definitely would not have been without consequence. A block of metal was not hollow, which was not the case with his skull or rib cage. His soft tissues were not prepared for such a test, even with his Stone Skin Skill.
Sure, he would have survived, but he would not have been able to carry out his genius plan. Speaking of genius plan, phase one went pretty much as planned and he was already reveling in the reaction that this Zhorrion priest would have when he triggered the second trap.