Additional information (as well as new official art) has surfaced in regard to the new Dusk Form of Lycanroc from a CoroCoro leak and a new Japanese promotional video.
Rock -Type. Its height is 2'07'' (0.8 m), its weight is 55.1 lbs (25 kg), its ability is Tough Claws and it gets both Accelerock (Midday Lycanroc's signature move) and Counter (a move that Midnight Lycanroc learns but Midday Lycanroc doesn't).
The new information also provides final confirmation that Dusk form Lycanroc is an event Pokémon only, akin to Ash-Greninja (and with the same reasons for existing, to be perfectly honest). Dusk Lycanroc cannot be found in the wild and no wild Rockruffs found in Ultra Sun and Ultra Moon can evolve into Dusk Lycanroc. The only way to obtain this thing is by evolving a special event Rockruff that will be distributed over the Nintendo Network between November 17, 2017 and January 10, 2018, for Ultra Sun and Ultra Moon only (obviously).
The video below is the Japanese promotional video introducing Dusk Lycanroc - both regarding its game and anime appearances.