If you’ve ever played a Metroidvania-type game, you know that you’ll have to backtrack a lot to reach certain places. Another common theme in these types of games is that as you progress, you’ll often be given ways to reach areas in older locations that you couldn’t reach before. This is exactly the case with Prince of Persia The Lost Crown. You’ll need to use the Lost Key if you want to use the elevator that takes you to the hidden floor. Don’t worry if that sounds like too much, here’s a full breakdown of what this key does, where to find it, and how to use it.

According to the item’s description, “Provides access to a hidden floor in the Citadel Elevator.” This description doesn’t give us the answer, but it does at least give us a clue as to how to use it in an elevator. The good news is that accessing this floor unlocks the Hidden Room achievement. So one thing’s for sure, your efforts won’t be completely wasted on something trivial.

You can buy the Lost Key from The Scrapper. He is a vendor who will sell you equipment in exchange for Xerxes.

Now that you have the key, it's finally time to use it to access the floor.