Map15: Obscure Base Part III: Rocks and Stones (Prodoomer)

This large and circuitous level introduces the Plasmagel plasma gun and a deadly miniboss type enemy called a scourge, which you must fight almost immediately. Since it has two hitscan attacks that can take off most of your health easily, it's best to stay out of its line of sight entirely and use indirect attacks.

The red skull switch room offers a good opportunity to dispatch the high level imps by casting Blizzard, Telekinesis, or Rays into the pillars.

When swimming through the mine-laden waters to reach the blue keycard, you can destroy the sea mines both by casting Sandbags at them and casting Telekinesis in their direction. The deeper you are in the water, the more effective the latter will be. Be aware that yes, you can drown if you stay down too long.

Towards the end of the level is a long elevator leading up to a control room and hangar, where a horde of tough enemies, including another scourge, is waiting to ambush you. Stay at the bottom of the elevator shaft and use Tornadoes, Blizzard, Electric Bow, or any other indirect attacks you have to clear out the room without exposing yourself.

Average Payout: 4,700 credits

Secrets
1. On the west side of the first outdoor area is a false wall. Crouch to get through and collect the treasure.

2. In the room with the red skull switch and eight pillars with imps, search the south wall on the east side for a secret.

3. When you get to the base on the eastern side of the map (guarded by zombies and cacodemons) take the elevator up the tower and get onto the perimeter ledge. Check the west side for a hole you can drop into and find some ammo.

4. In the room near the end of the level with the arch-viles in the center, check the northeast corner at the top of the stairs for a secret door. To get inside and collect the armor, you'll have to double jump and then crouch.

5. After clearing out said room and pressing both switches, go back down the elevator, kill the kamikaze that comes out, and check the area it was hiding for some treasure.

6. Backtrack a little more and you'll find a secret compartment to the west has opened. Get the ammo.

Secret Item
Come back to this stage once you have the remote control upgrade for your rocket launcher. Go to the lake that leads to the underground river where you found the blue keycard, and rocket jump onto the high ledge. Check your automap and examine the south wall for a small gap in the border line to the left of the underground river. If you look up at this wall, you'll see a false section. You can't actually rocket jump into this corridor, but your projectiles can still pass through. You will have to fire a guided rocket into the hole and carefully steer it through a mile of twisted tunnels to strike the target at the end. If you manage to pull this off, it will open a secret area in the starting area of the level, revealing an upgrade. Note that you can actually save and load the game while piloting the rocket, in case you make a mistake.

Rings
30 After opening the exit path to the level, go back to the watery underground area near the beginning where you were ambushed by high level zombies. The compartment at the top of the stone stairs to the east (where you killed a lost soul) will have opened, revealing the ring.