We've just rolled out a change to how players are locked-in to Quests and Events. Previously, players would be locked in to a specific instance of a quest/event as soon as it showed up in the Upcoming section of the Quest Board. This meant that even if players moved realms before the event actually started, if it had already showed in upcoming they would be competing in the quest from their previous realm. Moving forward, players are only locked in to a specific instance of a quest/event once it starts. This means that you can move realms at any time before a quest/event actually starts, and find yourself in the quest/event in your new Realm.