That's pretty well thought out, especially using the Haunted Castle again. I like how merciless she was in taking out Simon but (sort of) sparing Richter showing both sides of her personality as well as just basically tormenting Luigi, it just shows he can never catch a break.I thought of this one all day, and while I was busy reviewing for finals, I was beginning to think of a hypothetical Morrigan trailer. So...here it goes. Feel free to criticize but don't be too harsh.
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The scene begins in Dracula's Castle. Continuing from where we left off with Luigi and the Belmonts, they begin to traverse the castle. Then, out of nowehere, a figure then attacks Simon from behind, akin to Ridley's trailer complete with the red background and the silhouette. This is followed by Richter getting knocked out by a similar figure, only this time, the figure kisses Richter before knocking him out. The same silhouette and background appears.
Luigi, terrified, slowly turns around, shivering in fear. Then, he is punched both sides by the two figures. When Luigi regains his sense, he sees the image of a red and pink figure in front of him, before the figure disappears, passing through him. He turns around to see his attacker, extending her wings and locking her eyes towards Luigi. And then...
Morrigan allures the competition (that was the best one I found sorry)
Followed by...gameplay footage. Then it transitions back to the scene. Luigi is now begging for his life, when all of a sudden...Captain Falcon appears! Both him and Morrigan then focus on each other and prepare for battle, during which, her unique mechanics may be shown.
At the end of it all, Falcon, defeated, is then approached by the succubus. She gives one last look, before she kisses Falcon on the cheek, then takes him with her as she flies away.
Luigi, now recovering, assists the Belmonts, and then the trailer ends.
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I actually didn't know that she can split in two, and phase through enemies so your trailer would also show of some interesting abilities of hers too.
Overall I really like it, and I honestly wouldn't mind too much if Morrigan makes it in Smash (also your reveal title sounds great no need for apologies)