Spring Cleaning ("It's summer!") and a Story Idea Needing Help

Yes, Ms. Sparkle, thank you for the reminder.
Anyway, greetings.
To those whose stories were, or still are, on my Read Later list, due to said list growing rather quickly in size, and due to my frequently finding more stories of which to partake, I have recently begun downloading these stories to an external drive, both so that I can better control my RL list, and so I may read these stories even when my Internet connection fails.

Also, I have had a story idea simmering in my mind for a short time, and wish for some feedback/additional ideas/general thoughts about it.
Premise: A typical "dark, malevolent force" is invading, likely seeking to overthrow all that inspires good and light. It already took Princess Celestia's student and diplomat, Ebon Resolve (placeholder name), possessed him, and turned him into Sombra, who changed his diplomatic post to the Crystal Ponies into a dark dictatorship; now, with an actual base of operations, Equestria is in peril.
Goal: Princess Luna uses both the Somepony Has to Die and the Zero Approval Gambit tropes, using her lunar magic to trap this evil in herself.

Assistance and help are welcome.