
Holy heck that was an episode and a half.
I wouldn't have thought that a genuinely "epic" story like this one, so chock-full of backstory and organic worldbuilding the likes of which we haven't seen since pre-Crystal Empire, would be a ripe platform for self-effacing metahumor. Like:
- Pinkie teasing the "Smile" song
-

- "A Rainbow Dash/Pinkie/Griffons episode? This is clearly about Gilda, so I should just stay out of the way. Doesn't mean I have to like it though.

"
- reading Rainbow
-

"It's a little known secret that if you befriend a librarian, you can usually find out anything!"
-

Friendship

And plenty more. I love how much AKR is getting into the idea of this whole "interactive writer" schtick, like she's as excited to see all this in its final form as we are (she probably is!). Lord knows seeing what the animation team makes of her script has got to be a huge and awesome treat. I doubt she planned for the Griffon architectural style to be based on them all living in giant birdhouses and cuckoo clocks, but god damn does that work well.

And that "edgy" flashback art style, wow! Pretty freakin' great if you ask me. It makes for an episode of Pony that blends the mysterious and the foreboding and the threatening with that S1 world of cake-baking and songs, and it does it in a way that would probably seem downright bizarre to someone who's new to the show and just jumping into it right now, but it can get away with it for longtime watchers for whom that juxtaposition has been slowly building over the years from the cartoony injokey threat of Dragonshy to the Disney Princess villainy of ACW, to the Tolkien-lite threat of Sombra and the S4 stakes that ran the gamut from the Mane-iac to Tirek. Between The Cutie Map and this, S5 seems to be taking on the challenge of coming up with a level of adult "seriousness" that's well above the cartoonish stuff of previous seasons, but at the same time is concertedly maintaining links to its roots through a) lots of injokes and callbacks, and b) plenty of emphasis on desserts and dresses and the things that remind us that for better or worse, this is a kids' cartoon, and one in which the tone of happiness and sweetness is as much grounds for completely sincere storytelling as it is a source of tongue-in-cheek jokes about its own genre.
I'm also really impressed that the writers did this much homework in tying in the Griffon world to mythological sources.

Very nicely done.