You could theoretically play as Bhaal. There is no solid description of him/her, and even if he was male, he could be forced to take on a female form.
The main plot could be about the Sword of Mask and the Time of Troubles, and a way of sowing the Bhaalspawn seeds.
So you begin after the Tablets of Fate are stolen, somewhere in the Wilderness. You find that the other Gods have de-ascended, and you have to kill them. Ypou begin gathering factions to you (a stronghold) whilst searchign for the Sword of Mask. Cyric finds it first, kills you, and the rest, as they say, is history
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