However, students generally could not accurately assess the duration of an effect. For the sake of uniformity, the rules were therefore set according to a one-month effect period for a Five-Star Card.
As for why the number of cards that could be fused was cumulative, that involved something called stability. If a Divine Domain went without fusing cards for a long time, it naturally became increasingly stable, allowing multiple cards to be fused at once, up to the limit of its stability.
But this changed slightly after the second year of high school. By then, students' Divine Domains had generally developed, and they stabilized faster after fusing cards, meaning more cards could be fused.
In other words, during the first year after opening a Divine Domain, only one card could be fused each month.
In the second year, two cards could be fused each month.
By the third year of high school, three cards could be fused each month.
After the third year of high school, if one could become a demigod, the limit would rise further. But if one still could not become a demigod, the monthly card fusion limit would remain the same as in the third year and would no longer increase.
Because of the special nature of those three high school years, they were also known as the Golden Three Years—the three years for laying a solid foundation. If one could not become a demigod after those three years, the chances of condensing a Divine Profession would decrease year by year. The later it became, the less likely one was to become a demigod.
Of course, this rule only applied to students at formal schools. Students who had dropped out could ignore it and use cards without limit to strengthen their Divine Domains.
But the consequence