The Crucible is a enemy gauntlet featured in Darksiders II. There are 100 waves of enemies in the Crucible, starting with the most basic of enemies before quickly escalating.
 How to Unlock
After Death completes The Foundry and defeats the Guardian, he will get a letter through one of the Tomes, unlocking the Crucible. Only the first set of waves are available at first, since later waves of enemies consist of creatures that Death will encounter later on in his quest.
After completing five waves of enemies, Death will have the option of taking a reward, or continuing on with the gauntlet. If he chooses to take the reward, the gauntlet ends right there and he will get that rare piece of loot. However, if he chooses to continue he can make it to a later part of the crucible and gain an even more rare piece of loot. However, if Death falls in battle while going through a later wave, he will leave with nothing.
The first groups of enemies consist entirely of creatures that are found within the Maker's Realm. As Death makes his way deeper into the gauntlet, he will start encountering enemies found in the other areas of the overworld.