The Hero Trials is a rigorous exam that inspiring hero undergo to become members of the Hero Clan. The exam is so intense that each year applicants die.
As stated by Madam Fullmoon in the past the Hero Clan leaders sought out inspiring heroes based on their past or origins. However, in the modern era the Hero Clan executives seek out heroes based on their skill set and abilities.
It is assumed that each stage of the trials is held in different districts, however the one Kasha attended in only taking place in one district, Cloud Garden. The trials also serve as a way to filter out the good and bad applicants in order to prevent the clan from rotting within.