Although it's existence has been known about for some time in fan circles, Marshadow, the 802nd Pokemon was officially announced by the Pokemon Company just a few days ago, and will be coming to Pokemon Sun and Moon. A brief 16-second teaser was released on the official Pokemon YouTube channel showing off how Marshadow looks in-game.
Here is the trailer:
Unfortunately, details are scarce on Marshadow, namely in regards to when trainers will be able to battle with it. But according to Bulbapedia, Marshadow is a hybrid Fighting-Ghost type with High Attack and Speed stats and is set to make an appearance in the 20th Pokemon movie, the Pokemon, I Choose You remake.
If history is any indication, Marshadow will either be a timed event giveaway via download or QR code or a code that you'll have to pick up at GameStop. More details are "coming soon," according to the trailer, so we'll let you know when there's more.
Source: [Pokemon YouTube]