Those who conquered Calamity Ganon in The Legend of Zelda: Breath of the Wild will receive help in Hyrule Warriors: Age of Calamity, as save data from the former can be used to unlock the training sword in the latter.
Age of Calamity is the upcoming prequel to Breath of the Wild, which follows the events of the Great Calamity. In Breath of the Wild, Link wakes up after slumbering for a century and discovers Hyrule in ruins. If the player follows the story and watches the flashbacks, they will learn that Calamity Ganon defeated the Champions of Hyrule in battle, forcing an injured Link to enter a healing chamber that kept him asleep for years. Princess Zelda was forced to hold him at bay until Link awoke. Age of Calamity tells the story of that conflict and will give gamers the chance to play as the Champions of Hyrule.
Nintendo previously revealed those who pre-order Age of Calamity will receive a special ladle as an in-game weapon. There are more weapons available to fans of the series, as the Nintendo of America Twitter account has confirmed that Switch owners with save data from Breath of the Wild will receive a training sword as a weapon for Link in Age of Calamity.
It's likely that most Age of Calamity players will receive the training sword, considering that Breath of the Wild is the fourth best-selling game at the Switch. Chances are, the fans of Breath of the Wild will be interested in checking out its prequel, so a lot of Links will have the training sword.
It bears mentioning that Nintendo might not be doing a great job with these promotional items. Usually, when a company wants people to pre-order a game or offer other incentives, it's for items that players really want. All Age of Calamity players have been offered so far is a cooking implement and a wooden training sword, which are hardly must-have items. Where are the weapons from the other Zelda games? Where are the items from other Nintendo franchises? Those would be far more effective at bringing in the crowds than ladles and training swords.
Hyrule Warriors: Age of Calamity will be released for Nintendo Switch on November 20, 2020.
Source: Twitter