The Crom Faeyr is the best weapon in the game. I would strongly advise you to wield it, even if you are not proficient. It increases your strength to 25, so the to-hit and damage bonuses you will get just from having it equipped, even if you wield it in your off-hand, will more than offset any penalties. And the strength bonuses will apply to BOTH weapons you are wielding.
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Memnoch - Custodian of the Order of the Holy Flame 