The first batch of spoilers are out.
Not really a fan of amass.
I like this card, though:
http://mythicspoiler.com/war/cards/fluxchanneler.jpg
This should be able to generate some interesting shenanigans, including Parallax enchantments.
http://mythicspoiler.com/war/cards/ravnicaatwar.jpg
This one is interesting with Painter. Choose a color they don't have and wipe their board. Two Painter with different colors would wipe out all permanents on both sides, but that would be more of a fringe play.