DonnEll
wasn't yenxa at the 3rd evolution, even if a god took control over yenxa's body, it shouldn't be possible to defeat souta who is stronger than peak 4th evolution
It is like an upgraded version of possession skill. In possession, saya will possess souta's body increasing his speed, defense, and strength. There was even a time when saya completely possessed souta to injure a tier3 monster. The only difference is emperor probably had high level possession skill that increased yenxa's ability.