The grimoires

The book that chooses the mage, not the other way around: every fifteen-year-old receives one at the Grimoire Tower, and the number of leaves on the cover clover has become a scale of worth.

Three leaves for the ordinary, four — faith, hope, love and luck — for prodigies like Yuno. The fifth leaf is the devil, and the five-leaf grimoire that reaches Asta at Hage is the exception the whole series rests on: a black, dust-covered book for the one boy in the kingdom with no mana at all.