Master Level, Divine Realm, Legendary Class, Battle Legend...
Different worlds had different names for this rank, but there were also universally recognized standards.
"Only those who reach the pinnacle in a certain field, touch upon the origin, and bring the power of laws under their own control deserve this title."
Based on the information Su Hao had browsed using his League Champion authority, a simple and clear analogy would be this.
Master Zhang Xuan of the Divine Land Alliance had a Master Level Natu as her partner. It had touched upon and glimpsed a trace of the origins of space and time through the power of the Mythical Pokémon Jirachi, allowing it to successfully advance to Master Level.
Master Semin of the Sakura Nation Alliance had a Ninjask that had touched upon the origin power of speed—or perhaps flight and wind—thereby becoming Master Level.
Unfortunately, no matter how fast it was, it was completely countered by Cresselia's Dream Field. The moment it entered the domain of the Dream God, it had already lost.
But that was only one of the prerequisites for advancing to Master Level.
The second condition was actually quite simple.
Why should an ordinary Pokémon possess power that only Legendary Pokémon had the qualifications and ability to wield?
Naturally, it needed to temper itself, achieve a transformation in its Life Level, touch upon the Life Level Legendary Pokémon possessed from birth, and combine that with its comprehended Origin Power. Only then could it be considered a true Master Level. Neither condition could be absent.
This was also why so few beings in this world had broken through to Master Level.
The requirements were simply too harsh.
However, the arrival of battle systems such as Mega Evolution, Gigantamax, Terastallization, and Z-Moves had lowered the threshold slightly. Many Pokémon