52 war of the spark spoilers have started coming out. The cards look sweet so far.
Proliferate seems to be back and either the shown card has a typo or that ability has gotten just a bit better.
Also, there is now a card that gives your creatures and planeswalkers affinity for artifacts. Which is a VERY scary ability that broke standard at least once. Even better is that its in the colors of my artifact deck

There is also a black card that allows me to play the top card of my library using life instead of mana, making it pretty much perfect for my erebos deck

And a slightly worse blitterblossom. Which, for reference is a 25 Europe card at its cheapest.
Oh, and every creature with changelin now also counts as an army.