Microsoft is giving the full version of Killer Instinct to "dedicated" Xbox fans free of charge.
Xbox owners across various regions have received the gift via e-mail. Microsoft has confirmed the promotion is legitimate and said that it targets users with a variety of criteria including Gamerscore and Xbox Live tenure.
Some Xbox users have even been gifted an Xbox One console for free.
The email reads: "You're a fan of us and we're a fan of yours. Thank you for your dedication to Xbox. We want to show you our appreciation so we're giving you Killer Instinct.
"We've unlocked all characters so you can hit the ground running. Watch your inbox on 22 November for instructions on how to claim your free gift."
Killer Instinct is a reboot of Rare's classic arcade and Super Nintendo fighting game. It will release for Xbox One at launch (November 22) and will be free-to-play with a single playable character - Jago.
A 'Combo Breaker pack' will include the first eight characters (the six launch characters, plus the two next characters before their official post-launch release) for $19.99 / £16.99 / €19.99.
Alternatively, the Ultra Edition ($39.99 / £34.99 / €39.99) is described by Microsoft as "the best value for Killer Instinct fans". As well as the same eight characters from the Combo Breaker pack, it will include character accessory packs, character costumes and the original "Killer Instinct" arcade game.
A new trailer released last week revealed Orchid and Spinal as the latest confirmed characters.