Ple-Sen
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On the cover is the main villain (presumably the one who will later be known as Kha-Belekh). But this doesn't really resemble Mikhail (Misha looks more brutal), nor does it resemble Sarah (because, judging by the name, it's easy to conclude that Sarah is a woman). Perhaps it's either an old concept art of Misha, or the cover is a fake, or this character hasn't been mentioned yet.