You do not play any MK games on MKO, that's the part that confuses some newcomers. We just discuss things, post nonsense and the occasional serious posts in the General Discussion forum. Not much news for MK, which is why the place seems to be dead, or put in stasis.
You can't download or play any MK games here, but check out the Kombat Fight League if you're looking for something to do. If you do own any MK games for consoles, try the Gameplay & Matchmaking forum for online matches.
