Watch Merlin Season 5 Episode 12 Online Diamond of the Day - Part 1. High in the mountains a great horde gathers; Morgana prepares for war, a vengeful Mordred at her side. Merlin feels the weight of his destiny like never before as the ancient prophecies play out with terrifying accuracy. Yet before he can save his beloved Camelot, he must save himself. For Morgana wishes to destroy not just the kingdom but also Emrys.