MAP28: The Absolution (Doom 64)

MAP28: The Absolution is the last level of Doom 64 encountered during single-player mode. The layout is simple: You start off in a room containing all the weapons including the Unmaker and a large amount of ammunition. Leaving the room (the door cannot be re-opened after leaving), you will enter a courtyard with a pillar-like object in the center and 3 small "rooms" which cannot be entered and have a switch each next to them. The focus of the map: survive an onslaught of enemies, and then fight the Motherdemon. The key strategy will depend on whether or not you got the demon artifacts. The three unique switches are positioned north, east, and west of your position of entry to the courtyard.

The only way to activate the switches is with the demon artifacts (you don't lose the artifacts from your inventory). The more artifacts you have, the better your survival, since the switches open doors with switches that close some of the demons entry points. Closing all demon entry points will instantly lower the center pillar (it lowers normally if all demons are killed), revealing a megasphere that respawns indefinitely. The megasphere also occasionally switches to mega armor. The Motherdemon follows shortly after the pillar lowers. The only cover from her attacks are the pillar with the megasphere and the "rooms" in which the hordes of enemies spawned from.

To kill the Motherdemon, use the fully-powered Unmaker or the BFG9000. The mastermind should be killed easily provided you have both weapons in your arsenal.