Ainigmata Ostraka

Ainigmata Ostraka (riddle shells) were a series of scrolls found by the Spartan misthios Kassandra during the 5th century BCE. Hidden in temples, ruins, and such, the misthios would find treasures containing drachmas, weapons and gear.

The Riddles
The Ainigmata Ostraka were a set of riddles in various places across the Mediterranean Sea.

Reference

 * Assassin's Creed: Odyssey