Stelios's decision to turn on Zernon is not unfounded. He was already in trouble losing 60% of himself. Losing 39% has pushed that to doomed. He can't heal right now. He already sacrificed everything he had including his divine lords to become stable enough at 40%, so there is nothing he can do now except to have a bump in power.
He felt a pull on himself when Helios came to the divine kingdom last time. His separate body parts tried to reunite. He could resist Helios back then but that has changed now that he is too weak. He will have no choice but to be imprisoned in that jail in Helios' Stigmata if Helios comes to the divine plane again.