Dota 2 is the second (third?) version of a Warcraft 3 mod called “Defense of the Ancients”. It’s a game of the Multiplayer Online Battle Area (MOBA) genre, and it’s played 5 vs 5, either against human or AI opponents. There are over 100 heroes to choose from, which gives the game a great deal of replay value.
I’m currently running a Dota 2 blog, focusing on making lists of everything Dota2:
http://dota2lists.blogspot.ca/p/post-index.html