Mantis is a side mission available in Starfield after you pick up a Secret Outpost Slate.
Your objective is to find the secret outpost at Denebola 1-b and get the Mantis suit and unlock a new Mantis ship.
Here’s a walkthrough and guide of Mantis in Starfield.
To begin the mission, you need to have picked up a Secret Outpost slate during a main mission. Read it and you’ll know that it’s at Denebola 1-b.
Head to Denebola
You should see Denebola on your Starmap, located just east of Cheyenne. Head there.
Land at the secret outpost.
Enter the secret outpost
When you land in the area, you’ll discover some hostile Spacers. You can defeat them all first.
Make your way into the outpost known as the Lair of the Mantis.
Explore the Lair of the Mantis
The main objective is to explore the Lair of the Mantis. There’s also an optional objective to find out what happened here.
Inside, you’ll come across plenty of enemies to kill.
Remember to check each body as you’ll find some relevant notes like Leon Voclain – Sic Semper Tyrannis.
Continue down the stairs and take out the Spacers.
Keep picking up more notes.
At one point, you’ll even face a level 38 Space Vulture.
(Optional) Talk to Livvey
You will also meet Livvey who belongs to the opposing side.
Here, you can choose to either kill him or work with him.
You can work with him first, but he’ll betray you and somehow kill himself.
How to solve the Mantis puzzle with tiles and turrets
After meeting Livvey, there’s a room you need to go through filled with tiles and turrets that will kill you if you get the wrong tiles.
There’s also a computer at the side for Master level hackers.
Otherwise, you just need to step on the correct tiles.
The answer was in one of the notes you picked up: Tyrannis.
Just step on the tiles that spell out the word Tyrannis and you’ll make it through.
At the end, press the button to open the gate.
Continue to explore the Lair of the Mantis
Keep on going ahead and you’ll meet more enemies. There’s a turret in the first area.
Next, you’ll encounter robots.
To finish the optional objective, activate the automated message behind a door.
Continue ahead and defeat the Robot Models.
Once you’ve reached the area, Livvey will try to lock you in but end up blowing himself up.
Claim the Mantis’ Spacesuit and Starship
Finally, you can claim the Mantis’ Spacesuit and Starship.
Ignore the robots here as they warn you to leave.
You can go and activate the Mantis ship first at the end of the area.
Then, go back to the room and claim the Mantis spacesuit.
Go to the Mantis
Now, exit the area via the elevator nearby.
You’ll reach a locked door. Use the computer to open it.
Go outside and head back to the launchpad. You’ll see the Mantis ship there. The mission ends here.
You can now board the ship and go to a shipbuilder to make this your default ship.