To get to the Peak of Vindagnyr, you need to start with the “Investigate the Strange Ice” quest objective. It’s given to you by an NPC named Iris. She’s at an Adventurer Camp between the Dragonspine pathway and Springvale. Once you have the quest, venture into the mountains and solve the “strange ice” puzzle along the way. There are two sets of three shard puzzles to complete and demolish in total. Solving these puzzles will take you through the base of the mountains, Entombed City, Starglow Cavern, and Skyfrost Nail, in that order. You need to solve all the puzzles and defeat all the enemies to unlock the Peak of Vindagnyr at Skyfrost Nail.