In Fire Emblem: Three Houses you train your students and help them to grow more skilled in battle. They will have certain classes, and you can change their class if you so wish. If you want some to become a dark mage, you will need a Dark Seal. This certification exam seal will allow a character to unlock the dark mage class and become a powerful caster.
How To Get Dark Seals
You can get Dark Seals by defeating Death Knight. This powerful enemy will show up in Chapter 4, Chapter 8, Chapter 12, and Chapter 18. You can either defeat him in battle or steal the Dark Seals from him. It might be a good idea to steal them, as this enemy is powerful, and might give you some trouble. In the earlier chapters, you may not have powerful enough units to kill him, and might be better off avoiding him until later in the game.
What Do Dark Mages Do?
Dark Mages are offensively focused casters, and they lack the healing and protection spells of other classes. It is also a male-only class, so keep that in mind if you are thinking about changing someone into a dark mage. Dark mages have access to the following spells:
- Poison Strike (Dark Mage only)
- Fiendish Blow (Dark Bishop only)
- Lifetaker (Dark Bishop only)
Dark mages have the highest magic stat of the intermediate spell-based classes, and can eventually become a dark bishop. They also get skill mastery bonuses of +2 Reason and +1 Faith. To become a dark bishop, you will need an advanced seal for the certification exam.