There you are Miss Chae! You did it! The Fire Signs! Makes a whole lot more sense than the fire sixes, yeah?

It's great to see your enthusiasm as you try and get the cage open. For the dots on the metal lock are indeed Stars, which are formed into constellations..

You are just a few taps away from freeing your brother Miss Chae! Your freezing brother who is turning bluer by the second.

You trace your wand over Leo and it lights up white, but as you wait.. nothing else seems to happen. The clue did say The Fire Signs, not The Fire Sign, so maybe you need all of them to unlock the cage?