(beat)
Twilight Sparkle: This isn't going to be one of those deals where you, y'know, take us out right after you de-power us, is it?
Tirek: Hmph. I lied to Discord; I can certainly lie to you. And you'd be naive to think that harm would not come your way eventually, directly or otherwise. But if your intention is to dictate the terms of your surrender, then I find them agreeable. Once all of your magic is mine, I will take my victory rampage elsewhere and leave you in peace, for a time. It is not as though you'll be a threat to me, after all.
(beat)
Twilight Sparkle: Fine. One extra-large order of alicorn magic coming up, in exchange for my friends.
Discord: What?!
Twilight Sparkle: And Discord.
Discord: That... wasn't why I was surprised!!
I like that you addressed the whole "What's to stop the villain from just killing the hostage after you give them everything" problem. It always bugs me when that happens.
TBF, the only people he's actually hurt after being weakened were the Alicorns. He's not really the time to hurt those he doesn't perceive as a threat.
When you have a lot of characters in a scene, it can be easy to forget who all are there. In my Saturday group, this can sometimes be the rogue, which in hindsight is probably to her advantage, all things considered.
Well, not quite that either. He's surprised that Twilight's player would give up everything for her friends. That's something Discord's player would not consider.
"That... wasn't why I was surprised!!" got a giggle from me.
I recall a superhero from Grrl Power who goes by the name of X, whose power is to be forgettable and invisible unless specifically pointed out. He works for the government doing spy stuff, including tailing certain questionable individuals.
As far as I know, that IS alicorn magic. A combination of all three that is more than the sum of its parts. I would have liked to see Applejack teach her earth pony traits in addition to Rainbow teaching her flying.