What is the most rare thing in Sea of Thieves?

Ahoy there, fellow pirates! Have you ever wondered what the most elusive treasure is amidst the vast expanse of the Sea of Thieves? Is it the fabled Chest of Sorrows, whose weeping brings sorrow to even the bravest of crews? Or could it be the enigmatic Ashen Chest, shrouded in mystery and guarded by fierce Ashen Guardians? Perhaps you've heard whispers of the cursed Chest of a Thousand Grogs, said to contain a never-ending supply of grog, but at what cost? But what truly stands as the most rare find in these treacherous waters? Let's delve deeper into the question and uncover the truth, shall we?