...as you can see, it's not all that mysterious. You likely have already figured out what these stone tablets are in the very first area!

Seriously, substitution ciphers ought to be a thing of the past now! Chants of Senaar, Tunic, and Heaven's Vault know what's up. There was a missed opportunity here!

□) What reference?
□) Is that a real thing?
□) Polybius apparently never existed as a game.

(I chose Option □, btw, with some help from Davey.)