What was \the prophency given to ahab by Fadallah? how does it come true?

Ahab has secretly brought along his own boat crew, including a mysterious harpooneer named Fedallah (also referred to as 'the Parsee'), an inscrutable figure with a sinister influence over Ahab. Later, while watching one night over a captured whale carcass, Fedallah gives dark prophecies to Ahab regarding their twin deaths.By the end of the book, only Ishmael survives, clinging to Queequeg’s coffin-turned-life buoy for an entire day and night before the Rachel rescues him.