'Bang!'
Elder Weng utilizes his Soul energy to combust his purest yang blood essence!
The energy released overloaded Elder Weng, bringing out the strongest state he could ever achieve!
The foundation for nearly living being bodies would be their yang or yin blood essence. These contain a massive amount of pure yang or yin life energy. With this, one can functionally live.
And by the process of either cultivation or World Spirit Master path, the yang or yin blood essence gradually evolves, gathering more and more qualitative energies.
If one were to link their Soul energies directly into the yang or yin blood essence, it would overload the bloodstreams, completely combusting it.
From then, one can achieve the highest state their prowess could possibly achieve!
However, the cost of it is incomparably severe and usually is only done in inescapable life-or-death situations.