There are 5 Hero Grades in Devil Book: C,B,A,S,SS.
The Grade can be increased by getting the high-grade Hero from Summon or by using Soulstone.
① Tap on 'Grade'.
② Tap the Grade you want to increase. (It can increase one grade through Soulstone, one by one).
③ Upgrade using Gold and Soulstones.
④ The Hero's overall ability increases as you increase their grade. Also, the Level Up Stat bonus increases,
and when equipped with an equipment, the ability of the equipment increases according to the Hero's grade.
The Hero's Active Skills will be opened according to Hero's grade.
⑤ Heroes can use the 2nd Active Skill after reaching the A grade.
⑥ Heroes can use the 3rd Active Skill after reaching the SS grade.
There is also a 'Grade +' function for each Grade. You can only achieve the Hero Grade by using Soulstones.
⑦ Select the + Grade you want to proceed with the upgrade.
⑧ Upgrade by using Souldstones.
⑨ When the Hero reaches Grade +, the Hero will get a Passive Skill.
The acquired Passive Skill can be checked in the Skill Tab.
⑩ Tap on 'Skill'.
⑪ Tap on 'Passive Skill'.
⑫ You can check and upgrade Passive Skills there.
※ The guide was produced in a separate test environment.
So, It may change depending on the update and development situation.
Thank you for your love and interest in the Devil Book~
Devil Book Team