"Eius causa discimus." What does that mean?

That's fair.

There were several stone tablets lining the walls in the corridors; maybe they'll prove useful?

Yes, the one on the right has the same words he was mumbling - and apparently has something behind it.

See if you can cut it loose.

Cutting that tablet revealed a secret key!

Geron seems to think it's magic.

Surprisingly, this key doesn't go into a door - look for any shallow locks in the courtyard outside the academy.

Putting the key into this strange ring has revealed a new puzzle.

Each of the symbols on the outer circle represent a different god.