While not her specialty, her profiency for illusion based magic is well enough such that few can claim to have ever seen the Witch of Mass destruction when she isn't masked by layers illusions and glamour. Being in her early fifties, she isn't quite keen on letting anyone apart from her husband (And even that took some consideration) see her without behind her illusions either, so her actual appearance is something you only hear about in rumours and old tales. Suffice to say, if you have seen her true appearance, you are either really close, or really lucky. Or unlucky, as the case may be.
She normally appears as a heavily stylized version of herself in her early to mid twenties. And when I say stylized, I mean stylized. There's not one strand of her blonde hair out of place, and the single braid on the left side is just a little too tightly wound, and the ribbon too perfect, to be real. The witchlike dress that she usually wears is always spotless and creaseless, or if it does crease it only does to enchance her look. Her bust is definetely a couple of sizes larger than natural, and her eyes are always dazzling. Suffice to say, it's abit like looking at a photoshopped supoermodel, only in real time. Those not used to her might find the effect to be somewhat uncomfortable.
Her unglamorised appearance, she appears, well, like a fifty year old woman. Okay, so that isn't exactly doing her justice. While she has aged somewhat grecefully, since she hadn't really be taking care of her physical appearance for the past decade, having switched to illusions a long time ago, she is decidedly less beautiful without her glamours, even after taking into account her age. While she still retains most of her teeth, they are mostly yellowish, with some black around the edges. Her once deep blonde hair has faded to a pale dirty yellow, streaked liberally with gray, and the braid is extremely frayed. Her eyes have lost that youthful sparkle, and her bust is...well, exactly what you'd expect to find on a fifty year old. For someone used to her illusions, the transition can be rather jarring.
Clothing wise, she tends to wear a black skirt with some sort of short apron drapped over the front, and a black vest over a white, slong sleeved shirt. Or, that's the general gist of it, though it's hard to tell which part is real and which part is illusion. If the weather calls for it, she would also sport a pointed hat. The overall effect has her looking very much like the traditional witch; in fact, if she had a broom to go along with it, she'd probaly pass straight for one. To the average commoner, anyway.
Of war and assets - The PCs Country has been engaged in a war with a neighbouring, stronger country. The war has been going badly for a couple of years now, and the king's court is starting to get desperate. The PCs have been sent as diplomats to seek an audience with Marissa and get her to join the war on their country's side, or failing that, bring either the Spark Furnance or the secret behind it back. Unfortunately, it seems the other side has caught wind of this attempt and they are going to be sending some men to waylay the PCs. To make things worse, it seems that a thrid party is also after the spark furnance, and are alot more ruthless in their methods. Just was well, they have to make it back with either the Witch or the Furnance before their country loses the war, otherwise the entire mission would be pointless. Suited for mid-level parties whose first line of action is not "Storm that joint and kill everybody."
Follow the explosions - The spark furnance is stolen. This shouldn't come as much of a surprise, considering how highly coveted the item was. What was surprising was that someone managed to steal it without triggering any of the traps or security measures around it. So, there's a mage powerful enough to dispell the Witch of Mass Destruction security measures, stealthy enough to enter her residence undetected, and is now out there with the magical equalvalent of a nuke. Marissa has to both cover up the loss as well as track down the person who stole it, both of which are completely contradactory. She couldn't send any of her sevants after it; it'd attract undue attention. Hiring any of the locals was also flat out. Too risky. And don't even start on law enforcement. The solution? Hire some traveling adventurers. This is where the PCs come in, hired by Marissa to track down the Furnance and retreive it. Of course, they'd be up against someone who is both highly trained in both stealth and magic, but no one said this is going to be easy. Retreving the furnance would bring considerable favour from Duchess Marissa, which would definetely come in handy later down the line. Of course, there are plenty of people out there who are after the furnance as well, so they would be facing alot of competition in the pursuit.