It all started with a tweet:

Ahead of the new winter wonderland even beginning oh so soon, Blizzard have treated us to this, 12 days of 12 prizes and today they have begun with a great treat for you D.VA fans out there, the best thing is all you need to do to win this prize is to simply ReTweet the link above, its that simple. Upcoming Prize draws will offer the Mei Motherlode Bundle, the Cute But Deadly Overload Bundle, a Sombra Sleepy Time Bundle, a customized Xbox One S, an GeForce GTX 1060 display adapter, and other really decent loot. Retweeting all 12 days will also get you an entry into a draw for the Razer Grandmaster Gaming Bundle grand prize, which includes a Razer Blade Pro 4K laptop and more Overwatch gear. Sadly this is only open to peoples living within the united States, so if like me you live somewhere other than there, go make some new friends ASAP.