- Estimated achievement difficulty: 3/10 with a guide; 7/10+ without [Achievement Difficulty Rating]
- Offline: 40 
- Online: 0
- Approximate amount of time to 1000: 20-30+ hours [highly dependent on guide usage] [Estimated Time to 100%]
- Minimum number of playthroughs needed: 1 of the base game with proper planning and 1 of the "Road to Gehenna" DLC included with the game
- Missable achievements: 7, explanation below in roadmap, listed here for reference - Deal With The Deceiver (30G), Hedging My Bets (30G), Solipsist (30G), Press The Serpent (30G), Silence The Serpent (30G), Take It With You (30G), Help From Above (20G)
- Does difficulty affect achievements: No difficulty option
- Unobtainable/glitched achievements: None
Welcome to The Talos Princple, a first person puzzle game that will really make you think outside the box, put your intelligence to the test, and possibly even make you question reality. This game has a ton of content, some very devious puzzles, and a story that is extremely engrossing and philosophical in nature. Based on the price of the game ($50) and the length of it (easily 25-30 hours of content), I am going to assume that if you're playing this game, it's because you actually want to enjoy it and its puzzles, rather than just complete all of the content with a guide. Like many puzzle games, you can just use a guide for solutions to the puzzles, but I am going to assume you're here to enjoy this game, so I have structured the roadmap and achievement solutions as such, but have still provided resources for puzzle solutions in the event you want them. Also, don't be deterred or overwhelmed by the amount to do and all of the missable achievements. It is a very manageable completion as long as proper planning is done, and the walkthrough below lays out a very logical and simple flow to ensure you get the completion without having to replay the game a second time. Let's get started.
As noted in the Introduction, don't be intimidated by the amount of missables and all of the content in the game. I am going to break the completion into very manageable steps that are easy to follow and will ensure you don't miss any achievements so you don't have to start a new game. You may want to read through all of the steps below once just to get a feel for the order of things, but just focus on each step as you go and there isn't much to remember.
Step 1: All Green, Yellow, and Red Sigils, and Stars
*Important* - during this step, DO NOT approach or enter The Tower. After you complete World A and take the elevator out of World A, you'll be outside in a snowy area. Worlds B and C are to your left and right, and The Tower is directly in front of you. Stay away from The Tower until you unlock Hedging My Bets (30G) later in this step.
The other important thing to be aware of in this step are the computer terminals you'll notice in the entrance of every puzzle hub. There are four missable achievements tied to interactions with these terminals. While it's fine if you interact with the terminals a few times, to be safe, you could choose to ignore them completely until this roadmap tells you to do so. I personally interacted with around five of them during this step before I knew there were missables, and it only saved me some time instead of making me miss any. However, I would caution you against more than five or six interactions, and as I said originally, you can play it safe and not interact with them at all during this step.
With those missable notes out of the way, during this step you'll get acquainted with the game, and your goal is to solve all of the sigil puzzles in Worlds A, B, and C, in areas 1 through 7 in each of those three worlds. Each world has a sign showing how many sigil puzzles are within, and they get crossed off as you complete each puzzle, so it's very easy to keep track and see what you're missing. The green and yellow sigil puzzles are relatively easier ones. Green sigils will be used to open up all three puzzle worlds (A to leave the world, and then to access B and C), and yellow sigils are used to unlock new mechanics in the hub worlds. The red sigil puzzles are typically much harder than the other two, and these sigils will be used to obtain two of the endings later on. While working on getting the red sigils, you'll want to make it a point to obtain Extreme Persistence Detected (20G) and Know Your Limits (20G), since they must be done while working on red sigil puzzles. Refer to both achievement descriptions to get both out of the way.
On top of those three types of sigils you'll be unlocking during this step, you will unavoidably notice stars both on the signs for each puzzle hub and in puzzles themselves. There are 30 in the game, and you will eventually need to collect all of them. You can very well choose to collect them all in each puzzle hub as you progress (which is what I chose to do), and they are also marked on the puzzle hub signs so you know how many are in each area. Collecting the stars involves some of the most critical and outside-the-box thinking in the game, so be prepared to really be put to the test to figure out how to collect all of the stars.
By the time you finish this step, you'll have unlocked Worlds A, B, and C, have obtained all five of the new mechanics with your yellow sigils, and have all 49 of the red sigils. You'll unlock all unmissable story achievements along the way, and conclude with the two missable achievements Solipsist (30G) (for collecting all red sigils without asking for help, which you can't do at this point anyway if you're following this walkthrough) and Hedging My Bets (30G) (for collecting all green, yellow, and red sigils without having enterred The Tower). You may notice the giant doors open in World C with a while light behind them, after you collect every sigil. Ignore these doors for now.
Step 2: Restore a Backup and Ask for Help
With Solipsist (30G) unlocked, we now need to restore a backup save to where we still had a red sigil left to collect, and ask for help. Return to the main menu, choose The Talos Principle, and choose Restore Backup instead of continuing your game. The top file should be your file with all sigils collected, and the one right under it should be the same minus one sigil. Restore that backup with one red sigil not collected yet. This will unlock Last Stable Version (10G). Assuming you went in order, you should be in World C's hub or one of its puzzle hubs. In the World C hub right by the entrance to puzzle hub 7 is an axe in a red case on the wall. Take the axe and use it to break the wooden barrier on the door right nearby, which will unlock Break Down Barriers (20G). Head inside the portal to go to a Messenger island, unlocking Sacred Grounds (30G). In here, there are four big metal domes. Each one has a puzzle to solve to open it. Do so, and use the two connectors with the two transmitters to direct the beams and open the door to the temple in the middle of the island. Head inside and solve one more puzzle to release the messenger. Now leave this area and return to where your last red sigil puzzle is. After entering the puzzle area through the purple barrier, you should be able to spot an altar of sorts on a wall nearby. Interact with it and choose to ask for help, then scan the QR code from the messenger to unlock Help From Above (20G).
That concludes this little detour of a step to unlock the missable Help From Above (20G) achievement. Now you should return to the main menu and Restore Backup of the save with all of the sigils collected.
Step 3: Computer Terminals and Missables
Now is the time when we're going to finally interact with those computer terminals, and the MLA (Milton Library Assistant, which I'll just refer to as Milton from now on) inside. There are three missable achievement directly linked to how your interactions with Milton progress - Silence The Serpent (30G), Press The Serpent (30G), and Deal With The Deceiver (30G) - but there is also a later achievement, Take It With You (30G), that requires you to reach an ending after having completed Deal With The Deceiver (30G). We will therefore unlock Silence The Serpent (30G) and Press The Serpent (30G) first, restoring a backup each time in between, and finish with Deal With The Deceiver (30G), so that we can proceed onward to get Take It With You (30G) later.
So now, using your save with all sigils (although it doesn't matter which save you use at this point), go into each puzzle world (A-1, A-2, A-3, etc.) and interact with the computer terminal by the spawn. There are way more computer terminals in the game than you need for these achievements, so don't worry about seeking them all out at this point. Just use the ones that are quick and easy to get to. As far as your responses are concerned, answer in a confident, logical, and rational manner. Stick to your assertions and don't let Milton talk you out of anything. You will need to interact with around 15 computer terminals to get to the critical point, which will be after you take a personality test, then talk with Milton, and then set up an admin account, and then talk with another person. After that, you'll get to a point where your two available responses are as follows, and this is where the paths for the three missable achievements branch:
What holes? There are no holes.
I accept that some of my beliefs face difficult challenges.
Refer to Silence The Serpent (30G) or Press The Serpent (30G) for the correct dialogue options. Follow the path for one of those achievements, and when it unlocks, quit to the main menu and restore your most recent backup. You'll unfortunately need to interact with all of the computers again to get to this critical point, but at least you don't have to worry about missing any achievements. Now get the other achievement above.
Once you've done both of those achievements, restore your most recent backup one more time, and this time follow the dialogue choices in Deal With The Deceiver (30G) to make a deal with Milton and unlock that achievement. This time, while you're interacting with all of those computer terminals, you can save yourself some time and also read (at least open) all of the documents on each computer too, since they're need for a collectible achievement. DO NOT restore a backup save anymore. You're now going to progress to one of the game's endings with Deal With The Deceiver (30G) having been completed on your current save.
Step 4: Two Endings
With Deal With The Deceiver (30G) done, it's time to move onto two endings, the first of which requires that achievement to have been done on your current save. Head into The Tower now, and use your red sigils to access each floor, ascending to the top. After clearing all five floors, you'll head up a spiral staircase outside up to a puzzle area high above everything else. This is a multi-level timed group of puzzles that you must complete before the storm ascends and kills you. After you complete it, you'll ride a fan high up into the clouds. Walk through the gate at the top of the stairs and interact with the computer terminal. Choose to download Milton into your mind and take him with you, unlocking Take It With You (30G), a highly missable achievement. This ending will also unlock Free Will (40G).
With that done, restore your most recent backup on the top of the list. You'll be back at the start of the Floor 5 puzzle in The Tower. You'll unfortunately need to complete this puzzle again. This time, after you complete the Floor 5 puzzle and go up the spiral staircase, you'll notice Elohim is commanding you to go back. DO NOT go through the purple barrier at the top to start the final timed puzzles. Instead, get to the top where the purple barrier is and stay there until Elohim is done talking. Once he finishes, go all the way back down (either go back down the stairs and take the elevator down, or jump off the side since there's no fall damage) and go back into World C, and now go through those big open doors with the light behind them. This will unlock Changed My Mind. (30G) and Eternal Life (40G).
Step 5: Third Ending
With those two endings done, restore your most recent backup (again back at the start of Floor 5 in The Tower). Now your goal is to complete every puzzle in the game. This is also when you should finish all of your collectibles (all of the logs for A Good Listener (40G) and all of the documents on the computer terminals for Thorough Researcher (40G); refer to each achievement for a list of both). You already have all green, yellow, and red sigils. If you don't already have all 30 stars, get them now (Blessed Messenger (50G) has solutions for them). You will also need to use the same axe you used in World C to get to the Messenger island, and redo the Messenger island puzzles in World C, and take the axe with you to World B and World A, breaking open those wooden barriers and completing those two Messenger islands as well. While doing these Messenger islands, grab the LOL (30G) achievement, since it is easiest to do it then.
Lastly, in Worlds A, B, and C, there is now a door with an open gate. Inside each gate is a gate that requires 10 stars to solve a puzzle and open, leading to a portal to a new world. These three new puzzle worlds each contain three grey sigils to earn from solving more puzzles, for a total of nine grey sigils. Also, at the entrance of each puzzle world is a sign that will say something like "5 * *." These three numbers you'll get are the code to unlock Floor 6 in The Tower, and they're random for each playthrough, so jot them down or remember them. Once you have all nine grey sigils and your three-digit code, return to The Tower and take the elevator up to Floor 1, quickly resolve this easy puzzle to get to the computer terminal, and use your three-digit code to unlock Floor 6. Take the elevator to Floor 6 and use your grey sigils to open the door. Head through it to finally unlock Blessed Messenger (50G) for the third and final ending. That should wrap up all achievements in the "base game."
Step 6: Road to Gehenna "DLC"
The Road to Gehenna DLC, which comes with the console version of the game, is accessed separately from the main menu. It's standalone content with four achievements. Three of them - Welcome to Gehenna (10G), First! (10G), and Ascension (20G) - are story related and can't be missed. The fourth achievement, Free Admin (40G), requires you to first solve all of the puzzles like you normally would, but then also obtain 10 of the available 16 stars. Note that you DO NOT need to collect every star in this DLC. You only need 10, so feel free to only collect the easier ones and skip the really involved ones. With 10 stars collected, you then need to return to the main hub and head around the back of the World 4 building. From there you can jump to a small island below you. Ride the fans to an island, then jump down to another island, and ride one more fan to an island with a puzzle to solve. Doing so opens up a new puzzle world. Solve all seven of the puzzles to get seven grey sigils. Return to the main hub central platform, go down the stairs on the side to a door where you can use your grey sigils to open it. Doing so unlocks Free Admin (40G). After doing so, use the main terminal to complete the DLC and unlock Ascension (20G), finishing this extra content.
The Talos Principle is, quite frankly, an amazing game. There are a ton of puzzles to solve, with difficulty that ranges from relatively simple to insanely tricky, but that makes it all the more satisfying to figure each one out. There are layers and layers of puzzles to solve, so you'll be busy for quite some time. On top of that, the story and the background you can get from all of the documents is incredibly interesting and thought provoking. For any fans of puzzle games, this game is a must-buy for sure. I hope you enjoyed your time with this game, and congrats on a great completion.