The final battle with Diablo takes place atop the Crystal Arch of the High Heavens after fighting your way through the Silver Spire to reach the Pinnacle of Heaven at the end of Act IV. With all seven Evils embodied in him, he is not an easy fight. Followers cannot go with you to the fight against him (except in Adventure Mode), so prepare yourself accordingly. The battle consists of three major phases, each of which can last as long as needed (as Diablo has no enrage timer). There are two Health Wells on the left and right sides of the central ring, but they are not available in phase 2.