Spoilers of course. My initial thoughts / review. Screenshots and other fun stuff.

Just as I had hoped, the box/keys seem to be the theme for the whole season. Also, why is Spike feather dusting with the room in this condition? Gotta clean up them books first, Spike.

Not the last time I thought "Poor Spike" this episode. I really have enjoyed Spike more this season so far as compared to previously in the show.

Ahhh! Right after I mention I'm interested in this place, the whole episode takes place here! Celestia and Luna's old place, eh? I wonder why they chose this location... SO MANY QUESTIONS.

Reasons #45 - #10,831 why I love Twilight ^

First thought: "Uh, context plz?"

Pinkie is great this episode.

I hate that bunny, man. The guillotine would be too swift for the likes of him.

I love this scene. It's so SpoooOOOooky. That music too. Great stuff, this.

"We must use the upmost care--" Yeeeah, I saw that coming.

Aw yiss, AppleDash brohoof! By the way, if neither of you are scared then why is it daring for you two to stay in here? Just asking.

Haha that's funny, the picture's eyes mo-- that's Granny Smith isn't it? ISN'T IT?

Remind you of any other staircases from the show? Also, out of context it looks like a time warp or something.

I love how Rarity doesn't seem scared at all the whole episode (until the end, anyway).

"The trapdoor slide is Luna's favorite!" Please give me fanart right now please please. This is too cute.

You'd think somepony'd turn around and see somepony here... Oh well. Funny scene is funny.

I don't know if it's just me but Fluttershy looked a bit creepy here.

This scene was just too good not to be made into a poster. So I made it into a poster.

This should have been pretty obvious, but it surprised me somehow. :3 Very enjoyable, the episode was.