How do I start the Isle of Skye expansion in Assassin’s Creed Valhalla?

To start the Isle of Skye expansion, you need to complete the “A Fated Encounter” quest in Ravensthorpe. This quest becomes available after you build Valka’s hut and complete the initial Asgard arc. Once done, you’ll receive a letter from Randvi that triggers the journey to the Isle of Skye.