Genesect has been officially announced. Even though we already know about it from the Game data.
Over 300 million years ago, it was feared as the strongest of hunters. It has been modified by Team Plasma.
– Pokemon Black Pokedex
Genesect is currently the last Pokemon in the Pokedex. It’s the first and currently only Bug type legendary (not counting Arceus with Bug plate). It looks a lot like Mecha Kabutops, haha. Its Pokedex entry even say it was around a long time ago before being modified by Team Plasma.
Genesect is an event legendary, and it’s currently not available yet. It will be featured in the 16th Pokemon movie that will come out next year.
Sort of like Arceus, Genesect has a set of special held items just for its use. These are the Drives, which change the type of Genesect’s signature move Technoblast; there are Electric, Fire, Ice, and Water drives.