I'm glad you had fun!
The crystal is just a leftover from the first version of the update, which I make in Portuguese so a few friends can play. I always end leaving smth behind by mistake lol. It's gonna be in English like everything else in the next update, don't worry xD
It's pretty minor but here's what they say, in case you're curious:
Lianna: This time there's an ice wall on the way.
Jeanne: I fear I may not be able to push it.
Shida: How about we try a Fire Element spell?
Lianna: Oh, good idea! It shouldn't be hard to melt it.
Cast Embers? Yes/No.