Why did Hades send the worst monsters after thadia?

Hades sent the worst monsters after Thalia as a way to undermine her and the prophecy surrounding her destiny. Thalia was a demigod with significant potential, and by targeting her, Hades aimed to disrupt the balance of power among the Olympian gods and their offspring. The monsters served to test her strength and resilience, reflecting Hades' desire to assert his influence and thwart the plans of the other gods. Ultimately, it was a strategic move to maintain his own dominance in the realm of the Underworld.