Directly to you from Twitter:
The #FEHeroes Voting Gauntlet: Shadow in the Mirror has begun! Join the army for the Hero you wish to support, then gain points for your army by winning battles. View the status of each matchup here: https://t.co/PCLRWIIhMA pic.twitter.com/uYXnDHKEdY— Nintendo of America (@NintendoAmerica) March 2, 2018
…Wanna play? Buy a 3DS.
That being said, click on Fire Emblem Heroes for everything you need to know about the game. 😀