Black Mesa – Past the One-way Abyss Fall Walkthrough (Multiple Achievement Props)

This guide is for one specific part of Zen with multiple achievement props. If you are trying a full run with either two of the achievements “The Rarest Specimen”, “The Plan”, and/or “Pepperoni Precipitation”, Then this will be for you! If not then it won’t be a problem at all and you can skip everything about this small walkthrough.

Guide to Complete Past the One-way Abyss Fall

The Prop Areas (Simplified)

  • The Rarest Specimen (The Purple Hat) Chapter 3: Unforeseen Consequences; by the transit system you first came from.
  • Pepperoni Precipitation (The Pizza Box of Dr. Horn’s) Chapter 11: Questionable Ethics; in the cafeteria.
  • The Plan (The Cyanogen) Chapter 15: Zen; Inside the desolated research bunker.


First, you must obviously get the props needed. I suggest only getting two of the items as the headache will be proportional to how many items you have. I recommend getting the Purple Hat and the Cyanogen as this was what I used, but, you can probably switch the Cyanogen with the Pizza Box if you have to. I will note though, this was only done with “The Rarest Specimen” (the purple hat) in mind, so you could probably try this out with the pizza box for “Pepperoni Precipitation” but it might not work nearly as well.

You must also have satchel charges in hand as these will be important in getting the items in question to its destination.

The Start

You must then be at this certain location in Chapter 15: Zen. It is a fair bit off from when you teleport into Zen, but after some beautiful/creepy exploration, climbing, and a little puzzle-solving, you will be there:

While it is blocked, the power source, or what I like to call, the Chuthulu Heart, is just around the corner in crowbars length, but the problem lies when learning the area is a one-way jump, making it impossible to legitly go back to the original area.

The End

As the picture shows, you need to first place the hat in front of the ledge and leaf that can carry you to the next area. Then you will need to put the satchel behind the hat. Once this is ready, you need to make sure the second item is close by, as you need to try and do multiple actions all in a matter of moments. I also highly suggest a physical save, as this could take some time to not only get the right angle but also for the errors that can occur.

Once this is done, you must detonate the satchel charge, grab the item, and fling yourself towards the other area. After that, you will need to be quick as the hat will be on the leaf, but it will be rolling slowly down to the depts of space. Place down the item (Whether it be the Cyanogen or the Pizza Box) and quickly grab it before it falls. And if everything was successful, you have completed this trial.

While this will take multiple hours just to get to this point, it is worth mentioning as it took me around an hour just to figure out the plan of action on this part. I hope this really helps someone in need and gets them through the tough problems this game can make at times.

Written by Bibi

1 Comment

  1. There is no need to use satchel charges to get multiple items across the one-way abyss. Just jump across with one item and continue playing as normal until you get the next teleport working. Immediately upon going through that teleport, go slightly left of straight ahead to the edge and look down to the left. You’ll see a pond area that you were at previously. You can speed-jump there and work your way back to the one-way abyss where you can carry the next item across.

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