He's just a soul-eater. He should be killing Mafs or Earth Elementals instead.
If this is Sab, then everything is fine with us, because then it turns out that we have two mana in prison, and Duur'Kar is doing well.
There's an opinion that Karis might have committed the act not of her own free will, but under the influence of the second Night's Daughter of the Dryad; after all, the Dryad's move isn't visible in the newspaper. But how could Amko be a Dryad if her block comes after the Maf's block? I don't remember what Revan said about actions arranged in order; if you look at it that way, then he could be the Voice. Or a detached forest girl who likes to stick her nose where it doesn't belong.