In the second chapter of Darksiders Genesis, you have to defeat a boss. To get to that boss, you need to open one of the passages. On this page of our guide to Darksiders Genesis, you will learn what you have to do to reach the boss.
The battle is in The Slag Heap location.
To get to the boss, you need to visit 3 locations with enemies. Simply jump to one of the platforms and go to the very end. There you will find several opponents - defeat them.
Do the same with the other two signs. To activate them, you must reach the end of the corridors and defeat the enemies.
Another new mechanic you will encounter is exploding walls. To destroy them you need to set fire to the Vorpal Blade and then aim it at the wall. This way you will activate all the signs.
When you return to the arena, you will encounter Slug Demon. This battle ends chapter 2.