Stubborn Mule

Stubborn Mule was a virtual representation of one of Kassandra's genetic memories, relived by Layla Hassan through the portable Animus HR-8.5.

Riddle
''If you climb to the peak of Mount Zas, you will see two smaller islands to the south. I can only be found on one of the islands in a pile of hay near a friendly donkey. Make a decision - the last traveler starved to death trying to choose between the two!''

Outcome
Kassandra found and recovered the treasure.

Reference

 * Assassin's Creed: Odyssey