Once all 3 Dragon Glass Tokens have been collected, flip the Ice Dragon Card to its “Phase 2” side and move the Ice Dragon to the domain with the Night King. The Ice Dragon moves with the Night King until the end of the game.
In Phase 2, after Evoking Terror (see Evoke Terror), the Night King and the Ice Dragon together move to attack the nearest castle that isn’t destroyed, controlled by White Walkers, or controlled by a Terrified House. If there is a tie for nearest, he prefers to move to a castle controlled by one of the players. If still tied, it is the players’ choice.
Immediately add 1 White Walker to that domain, If a player in that domain is able to battle the Night King then they must. If not, they must retreat (see Battling the Night King). If they lose or retreat, then the Night King gains control of the domain and the castle in that domain is destroyed (laid on its side).