Players are able to ‘unlock’ special chests which provide them with improvements for their Heroes and towers. These chests tend to be on timers so players can gain something for free simply by logging in every once in a while. The Tower Chest becomes available every 9 hours, while the Hero Chest is a 24 hour unlock. New quests become available every 2 hours. Some quests can take several seconds to complete making them an easy way to earn Hero Keys which can then be used to unlock more chests.