Yeah being bad in Reason is not gonna be fun. Hope she has good healing spells at least.
Doing an all magic run might be amusing too.
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Character build recommendation: I would actually recommend largely forgoing a magic class entirely you can go either straight assassin/Falcon Knight who uses Hexblade on the occasional unit with disproportionately low resistance. In which case I would pick up Death Blow from Brigand. Or a Wyvern Annette style build where Hexblade and Levin Sword is your primary form of attack, despite being in a non-magic class in which case pick up Fiendish blow from Mage. I prefer the former as Manuela lacks Annette's magic and Hexblade doesn't make use of Manuela's amazing speed.