On this page of the Halo Infinite guide, you can find a walkthrough for mission 3 - Outpost Tremonius. Our walkthrough will help you in reaching the surface exit, securing the Zeta Halo landing site, and landing the machine piloted by Echo 216.
Rendezvous with the pilot
You can find a Spartan Core chest right after starting the mission. These items are a kind of collectibles that are used to upgrade your gear. We recommend buying the Voltaic upgrade for Grappleshot, as it will allow you to electrocute and stun opponents that are hit by your grapple.
Proceed onward and expect a battle against standard opponents in the tunnel with the weapon racks. You need to use the console to open the hold door.
Clear the landing zone
You've managed to reach the surface, but you cannot explore Zeta Halo freely until you complete the current mission.
You should see the landing zone in the distance. Thanks to reaching the surface, you now have more freedom in chosing how to dispose of the enemies. If you have a sniper rifle or other ranged weapons, consider engaging your opponents from a distance. Moreover, you can now use buildings as cover. Don't leave the initial location yet, as there is another Spartan Core nearby.
The main path leads straight to the landing site, but you can look for other roads accessible using your Grappleshot.
After dealing with all opponents, use the console to confirm that you've captured the landing zone. A machine piloted by Echo 216 will arrive and you will pass the mission. Moreover, you've received some Valor - reputation points that will be used in the future to e.g. summon free vehicles, weapons, or marine support teams.