Headcanon: Shining Armor dying would cause both Twilight and Cadance to flip at the same time.
 
And then Celestia might go too, over the stress of having her former student get corrupted.

Your resistance only makes my apocalypse harder

Amazing work here! it would be really sad to see this actually happen though.

Bonus points for getting Conquest right. Also, headcanon accepted for what happens when four alicorns go Nightmarish.

@soundtea  
sees description
 
Well, 3/4 ain’t bad.

@PonyPon  
No, based on the actual Biblical verses in the source.

So, Twi is Death, I’m guessing Nightmare is Famine, Cadance is obviously War, so Celestia must be Strife Pestilence.