The Thunder Drake.

Sovereigns are a queer bunch. Just like there are weak titans because of their restraint, and there are strong titans because of their active embodiment, there are also different levels of Sovereigns. This is based on the complexity of their seed of power. The weakest sovereign is still on par with a grand god but the strongest sovereign can be as strong as a celestial god. Only a god King or the celestial supreme can tussle with an origin god.

The seed of power is the foundation of a sovereign. Even if a sovereign dies, the seed of power will remain. The seed of power is eternal. When a titan goes through the valley of the shadow of death and comes out of it, they create something eternal. Then if that Sovereign fuses with his seed of power, they too can become eternal. In a way, it is the greatest birth by the lower realm. The gestation of a mortal to birth an immortal.