"It seems the Third Prince really has no other tricks up his sleeve." As more time passed, Du You noticed that the Third Prince continued to slowly consolidate power. The pace got even slower, to the point where the nobility was consolidating faster than he was.
He must have signed that contract initially because he had a tier-six fighter in his hand.
Because he made a move, the tier-six fighter directly killed the enemy's upper class, which allowed him to use the Ragtag to put the Shenghai Kingdom on the defensive, then boost his reputation, consolidate the southern nobles' armies, and take down the Shenghai Kingdom in one fell swoop.
Such a prosperous kingdom, coupled with the clandestine training methods, meant that as long as the Third Prince didn't rebel, the throne was definitely his and no one could threaten his position.
What he didn't expect, however, was that the enemy's power was stronger than his, making tier-six nothing significant.
