You can now find Silver Keys in the levels that unlock small, mysterious chests. Inside these chests are Totems. Powerful items that will give you a power up for the rest of the map. Right now there are 9 different Totems which are all different playing cards, but in the future a whole lot of various items will be added with all kinds of new abilities.
You can read the full changelog of the current update here: http://steamcommunity.com/app/321270/discussions/0/496880503067662061/