Darksiders Genesis can be played alone or with a friend. Remember, however, that the maximum number of players is two. Check this page to learn how to start a split-screen/online game.
Summoning Stone - split-screen
Every map in Darksiders Genesis has a Summoning Stone. When you approach it, it will open and glow purple. One of the Summoning Stones is presented in the picture above.
Press the corresponding button to interact with the stone.
One of the options allow you to start playing in co-op. To do this, simply click on the option marked in the picture, and then summon a friend.
Summoning Stones also serve as a portable store. You will find items from unlocked merchants.
Menu - online
You can start playing in online co-op using the traditional method. Go to the menu and choose the cooperation mode at the bottom.