I finally had a moment of solace from school, so I'll join this one. Image, please.
This time, I have not one card, but three! I'm just entering this one, though, it's just that as I was designing this the possibilities of the other ones... increased; I had the idea a while ago, but finally being able to materialize the card helped me focus the concept so much more.
The basic concepts of Party Crasher and Unforeseen Curse go a while back, when I was designing my Mimikyu; of course, they were focused on Pikachu, but I thought they deserved better, so I left them out; conceptually, they'd be more appropriate for a Gengar, or some pokemon that actually does have a history of jump scares (Unforeseen Curse's original name), but thinking about it, I remembered one witch that has a habit of coming out of nowhere and throwing a curse on you just because: Maleficent. That, in turn, helped me focus more the concept of Light Mismagius, which I recycled from some event here a long time ago. If Dark Mismagius was going to recall Maleficent, it was obvious that Light Mismagius had to recall the Good Fairies (fairies, witches, who cares?), hence the two gifts. The Misdreavus is a very old concept I liked too much, but I couldn't fit into the theme of my set, so I left it apart, even though it was already done.
I wasn't sure about the wording of Party Crasher; of course, nothing like it has ever been done; it was originally more detailed, but I thought maybe I could shorten all that by saying that you'd be treating your opponent's bench spot as your own; I hope no loopholes are opened with that, but the intention is that using the ability essentially gives you a 6th bench spot, albeit one that can only be occupied by Dark Mismagius.
Dark Magic is simple, it's there mostly because I didn't want to have her attack only from the bench, and I couldn't word an additional effect if she was Active in Unforeseen Curse. It's for the better, really, it's complex enough as it is. Funnily enough, the exact same situation happened when I made my set's Mismagius; they even do the same damage. Had I had more space, it would have sent one of your opponent's benched pokemon back to the deck, to make room for Dark Mismagius.
Unforseen Curse is the key to all, of course; it's more straightforward than it looks, though; you can use it from the bench, and it does 50 and sleep (because of Maleficent, get it?), and if she's on your opponent's bench, the damage goes up to 100. Maybe a little too much, but I expect your opponent to take measures to keep Dark Mismagius away.
The double type is obviously because it's dark, which also answers for the low HP; it should be 60, probably, but the metagame (even mine, for which this card was designed) has gone up in damage, so a little bit higher just in case.