Level 23: Unholy Temple

Start by falling to the floor and following the left hand wall to a teleporter blocked by a bar.

Continue along the left hand wall to another teleporter, killing all Arachnotrons (you'll need to).

Return to the first teleporter and step on it.

Upon teleporting, kill all Spectres (you'll need to).

Turn left and follow the right hand wall to a green wall near a Blue Door.

Press C-Right to lower the green wall like a lift. Ride it to the top.

Turn right and follow the left hand wall to a switch, killing any Hell Knights in your way. Hit the switch.

Turn around and follow the left hand wall back to where the lift was. Turn left and drop to the floor below.

Follow the left hand wall to an opening and go through.

Head up the stairs at the other end of the room. At the top, turn right and go straight to the MegaArmor. Pick it up.

A new opening will appear; go through it. Find the switch on one of the pillars and hit it (watch out for Demons). The Blue Key will lower; grab it and leave the room.

Head back up the stairs, go through the opening, and follow the left hand wall to a staircase. Head down it.

Turn left, go through the opening, then turn left again and follow the right hand wall to a Blue Door. Open it and go through.

Follow the hall to the Red Key, killing any Lost Souls in your way. Grab the Red Key, turn around, and leave the room (watch out for crushing ceilings).

Back outside, turn left and follow the left hand wall to a Red Door. Open it and go through.

Follow the right hand wall to the Yellow Key, killing any Shotgun Guys in your way. The key will teleport when you approach it.

Turn around, and the Yellow Key will be across from you. Walk up to it, and it will teleport again. Turn around and follow the left hand wall to the Yellow Key. Walk up to it, and it will teleport.

Turn around and follow the left hand wall to a staircase, killing any Hell Knights or Shotgun Guys in your way. Head up the staircase.

At the top, turn left and follow the right hand wall to the Yellow Key, killing any Shotgun Guys in your way. Pick up the Yellow Key.

Turn around and drop to the floor below. Go straight to the door at the other end of the room, open it, and leave.

Back outside, kill the Cacodemon. Search the area for and kill any other Cacodemons (only 2 appear on low skill levels).

Return to the Red Door. With your back against it, go straight through the opening in front of you. Head up the stairs.

At the top, turn left and walk up to the Yellow Bars. Press C-Right to remove them.

Go straight to the opening at the other end of the room. Back up and run across the gap to the platform. Kill the Shotgun Guys.

Hit the three switches on the pillar in the middle of the room in this order: Red, Blue, Yellow. Leave the room (run across the gap again).

Go straight until you reach a staircase. Head down it and go through the opening.

Turn right and follow the right hand wall to a switch. Hit it.

Backtrack to the room with the three switches. Hit the switches in this order: Yellow, Red, Blue. Leave the room.

Follow the right hand wall to a staircase. Head down it.

Turn left and go through the opening. Turn right and follow the left hand wall to a pathway not surrounded by short walls. Drop to the floor below.

Turn right and follow the left hand wall to an opening. Go through.

Follow the left hand wall to another opening. Go through.

Take either path to the other end of the room. Kill the Arachnotrons that appear when you hear them warping. The door will open.

Return to the opening. With your back to it, go straight to the wall in front of you. The floor will rise. Hit the switch in front of you.

Turn around. Follow the right hand part of the Y-shaped pathway to an opening. Go through.

Kill the Hell Knight and hit the switch on the pillar.