By far one of the hardest and unique action RPG's I have ever played. In a way, it behaves more like a MMO with the PvP battles, co-op and the fact that you can invade other players worlds.

Another feature is that when you die, you lose all you souls and come back as a phantom, with your health cut in half. the only way to get your body back is to use a stone of ephemeral eyes (the easiest way), kill a demon (by yourself or with others) or invading another players world. when you return to the point where you died, touch your bloodstain to get your souls back.

The feature that really stands out the most and unique to the genre is that you can write messages and leave them in the environment for other players to see. So you know where you can find danger or treasure (however the message might be false). Also you can touch other peoples bloodstains, showing you how they died, so you can avoid the same fate.

It certainly deserves Gamespot game of the year 2009 and IGN's best of 2009.