What is the rarest monster in Sea of Thieves?

I'm curious, could you tell me what the rarest monster is in the game Sea of Thieves? It's a question that's been on my mind for a while, and I'm eager to find out. Is it a mythical beast that's shrouded in mystery, or is it something more common that just happens to be incredibly elusive? Whatever the answer may be, I'm excited to learn more about this mysterious creature and the challenges it poses to players.