The Dark Druid class is a class unique to Nergal, the main antagonist of Fire Emblem: The Blazing Sword. It can use all forms of Magic. He also has the highest HP cap of any human character in this particular game, at 75.
Nergal' stat: HP:75 Mag:30 Skill:18 Spd:15 Luck:20 Def:28 Res:30
He wields the spell Ereshkigal, one of the 2 strongest Spell in game. To defeat him, You should use Athos with Aureola/Luce, the S-rank weapon you get during the chapter or, if you trained an assassin, try to use silencer. You can use Nils and his ring to help you.