http://www.pcgamer.com/rain-worlds-difficulty-changing-update-is-now-in-open-beta-on-steam/

I really liked Rain World, but I'm also really bad at it, and so I ultimately moved on to other things without making very much progress. But now I have a reason to go back—several in fact. The 1.51 update, which was announced in June, is now in open beta on Steam, bringing with it new difficulty levels, multiplayer modes, and "new secrets, strangeness, and hopefully a generally smoother Rain World experience." 

The new difficulties actually come in the form of two new playable characters. The Monk, "weak of body but strong of spirit," will round off some of the game's sharper edges: "In tune with the mysteries of the world and empathetic to its creatures, your journey will be a significantly more peaceful one," developer Videocult said.