As far as I know the best item for raising charisma, if yours is low is the ring of human influence, found in the circus (loot from kalah).
Well the blade of roses raises your charisma 2 points but since you'll be a sorceror that won't help. I don't think charisma will prevent some npcs to go hostile if your reputation is low, but what do you want a low reputation for? you'll be soloing so you won't lose any npc if you get too high, even if you're evil it doesn't matter.
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