There's tiny added bonuses for prolonged levelling in CB for evils, the Felwithe banker is on the guard faction it seems (I forget which, but killing orcs does the trick). Check your con with the guards, get it to apprehensive or above - one decent session at the wall/TR might get you that far.
Later, when you're able to invis (Lvl 30?), you can invis to the bank...do your business, and invis back out. I say that because otherwise you'll be running past the Paladin guild and the annoying bard mail quest guy. The paladin guild pack a punch
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Don't try to bank in Kelethin however (tree city), that banker is just a full-time asshat and on a different faction from the guards. You'll still be able to sit by the guards and enjoy a cup of tea or piece of cake without them taking offence though.
Banking is handy on Faydwer if you'll be frequenting Unrest or Mistmoore (and Kedge at later levels I guess
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