Consistency

You take another look at your surroundings. You can't figure out how the lock works, and you've got nothing of significance on you, aside from your phone and that other thing. Neither of which seem useful. But maybe there's something inside the room...

Use the scepter of justice.

Yes! The scepter of justice! You thought it was just there to mock you, but it's perfect for prying the door open! You stick it in there and pull until the door pops off its hinges.

But wait, you can't just rush out. There are guards everywhere, and you need to figure out what they're doing before you can plan your next move. So, uh, what are they doing?

They are clearly singing "Sweet Dreams are made of these" and yet it's actually titled "Sweet Dreams (Are Made Of This)".

Oh. They're having a sing-along. But they're getting the song title wrong! How can you correct this grave mistake?

take a picture

That's it! You take a picture of the guards singing the song. Of course, when you finish, you realize that photographs, being a visual medium, cannot actually capture audial input, such as song lyrics. Well, darn.

Worse, while you were taking that picture you drew the attention of the Sphinx. It seems that it's waiting for you to answer its riddle. What was the riddle, again?

What do you have that I don't?

Oh, right. "What do you have that I don't?" Well, that's a stupid question now that you think about it. The answer is so obvious.

A rideable lawnmower

You have a rideable lawnmower! There's no way the Sphinx has one of those. You pull it out of your pocket and charge right through the Sphinx and the guards.

But wait, the Sphinx is mumbling something while it's lying there on the ground. What's it saying?

https://xkcd.com/1680/

Sounds like nonsense. Must just be rambling. There's no way this is some sort of additional riddle. Anyways, there's only one way out of here, and it's...

ctrl+v

The Control and V buttons on your rideable lawnmower! You press them both and once and fly out of the maximum security prison/ancient temple.

But now that you've escaped and claimed the Scepter of Justice, where will you go?