1.- I dont think Sarevok is inmune to magic
2.- Bhaal had more than one child from each race. In the final movie, each statue is a child of Bhaal, and there are LOTS of statues
3.- Just another child of Bhaal, the first one Sarevok kills i think, cause when hes gonna kill him Sarevok says: "i will be the last... and you will be the first"
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"I wish my Angel was here... I fear nothing with her" -Ertai, Captive of the Blinding Angel