Board Thread:Questions and Answers/@comment-200.43.89.194-20180205151222/@comment-26447088-20180206034420

Grimoires are levelling material. They're really easy to come by, especially since you can grind them from the bonus areas in quests and Gifting events give tons of them.

You'll want to use them to level pretty much everything, since it's a lot faster than using 1/2*s.