Now, one might ask "what are those butt-windows for?" and the answer, put simply, is "branding". See, when you're really good at making illicit poisons most ponies can't get their hooves on, you can set the price however you like, essentially. She's built up a nice reputation around her stomping grounds, so naturally some dopplegangers and copycats have arisen to try and pass off as her. These knock-offs, however, often sell brews that are terribly lacking in potency or are straight up non-functional. Wasumu didn't know this was happening at all until a local pony mafioso was sold bad brews by one of her dopplegangers. After some 'persuasion' (giving the mafia boss several extremely rare and expensive poisons for free), she devised these 'Cutie Mark Roll-up Windows' as a discreet way to establish her identity (and hide it again just as quickly). Now, when she sets up shop in some shady corner of town, she can show her marks to customers so they can verify it is indeed "Wasumu the Poisoner" they're dealing with and not a cheap fake. While some dopplegangers have continued to try mimicking her, they simply lack the artistic talent to paint her cutie marks on well enough to fool Wasumu's clientele.
On the subject of branding, Wasumu also started bringing along her pet cobra 'Zamaradi' as a traveling companion. Most ponies and would-be copycats wouldn't be brave enough to befriend a deadly Gemini Cobra, much less let it slither over their body freely. Zam's a sweetie, really, but she can also be very helpful in keeping would-be assailants away from her zebra friend. Others think twice when they see her fangs.
I actually finished this a few days back, but I hadn't uploaded her yet… so here ya go! Dunno if my OCs are exactly interesting material, but she's a fun character in my books and D&D pone games. I'll just keep working on my daily sketches; until next time, keep it classy, ponefriends ;)