Act 4 - Fortress

The Fortress is the final act of the 4. The enemies found here are Heretic Guards, Heretic Followers, Skull Guards, Guard Droids, Dark Servants, and Auto Turrets.

Level 3 and Level 6 feature a boss.

The Level 3 boss is the Arachnotron, a spider-shaped mech that is basically a larger version of the Giant Spider enemy from Act 3.

The Level 6 boss is Destruction, the final boss in the game. It is a giant mech with several different attacks, but is rather slow and easy to play around.

Act 4 is also referred to as Heretic Fortress.