Borderlands 4 is packed with side missions that blend humor, satire, and chaos - and Flat Kairoser might be one of the funniest yet. As a Vault Hunter exploring the icy wilderness of Kairos, you'll encounter Skeptical Sam, a conspiracy theorist who's convinced the planet is completely flat. The mission is a tongue-in-cheek jab at "Flat Earth" theories, featuring plenty of witty dialogue, wild enemies, and a trek across some of Kairos' most treacherous terrain.

This guide breaks down how to start and complete Flat Kairoser in Borderlands 4, along with all objectives, locations, and rewards.

Quest Overview

·Quest Giver: Skeptical Sam

·Location: Southern Terminus Range

·Prerequisites: Complete the main mission, A Lot to Process

·Rewards: XP, Cash, Random Weapon (Uncommon to Epic), Vault Hunter Customization, ECHO-4 Customization, Eridium

You'll unlock this mission after gaining access to the Terminus Range. Skeptical Sam can be found south of the Grey Havenage safehouse. Once you speak to him, he'll eagerly explain his theory that Kairos is flat - and it's your job to prove him wrong through a series of ridiculous experiments.

Flat Kairoser Objectives

1. Take Flat Kairos

2. Stomp the dang globe

3. Follow Sam

4. Reach the Shrine

5. Reach the Wrecked Ship

6. Collect Surveying Equipment

7. Find a Suitable Launch Site

8. Place Atmospheric Surveyors

9. Activate Surveyors

10. Find the Balloons

11. Talk to Sam

Step 1: Take the Flat Kairos and Stomp the Globe

After the dialogue with Skeptical Sam, he'll hand you a small model called Flat Kairos. Once you accept it, Sam instructs you to destroy a nearby globe that represents the "false spherical narrative."

Climb up to the nearby roof marked on your mini-map. Stand above the globe, jump, and then slam down using your crouch button mid-air. The globe will shatter dramatically, and Sam will declare victory - for now.

Step 2: Follow Sam to the Shrine

Follow Skeptical Sam along a mountain path. Use grapple points to climb and prepare for combat against packs of Kratch enemies. At the shrine atop the ridge, Sam insists the horizon is flat, while your ECHO-4 readings prove otherwise.

Tip: If you've been upgrading your Vault Hunter with new mods or Borderlands 4 Items, this section is a great time to test them - especially weapons with Cryo or Shock damage.

Step 3: Travel to the Wreck of the Big Carl

Sam refuses to give up and insists the "real proof" lies in the wreckage of the Big Carl, a massive crashed ship in the frozen wastes. Follow the map marker to this new area, where you'll be ambushed by Rippers and Warhorns. Clear out the enemies before collecting the surveyor parts scattered around the wreck.

·Part 1: Next to an outhouse near the crash site.

·Part 2: On top of a twisted metal arch above the ship's hull.

·Part 3: On the roof of the main wreck, between two ammo crates (reachable with your grapple).

Once all three parts are collected, Sam decides it's time to "launch the truth into the sky."

Step 4: Find a Suitable Launch Site

Your next stop is the designated launch zone, high in the mountains. Follow your ECHO-4 marker, climbing several ledges and taking out groups of Creeps along the way. The final section features a large open area filled with enemies - clear them out before proceeding.

At the peak, you'll reach a massive skeletal structure. This is your launch site.

Step 5: Place and Activate the Surveyors

Now that you've reached the launch site, it's time to set up the three atmospheric surveyors. Interact with the highlighted spots on the ground to place them, then approach each device to trigger the ECHO-4 balloon mechanism.

When activated, the surveyors will float into the sky, capturing atmospheric data to create a planetary image - evidence that Kairos is, in fact, round. But of course, it's never that easy.

Step 6: Track Down the Balloons

After a few minutes, Sam panics as the balloons drift off. You'll now need to chase down and retrieve them before the data is lost.

·First Balloon: Travel to Shredded Summit. Follow the map marker and use your Digirunner to reach the area quickly. Clear out the enemies and shoot the balloon to bring it down, then retrieve the surveyor.

·Second Balloon: This one floats over the next ridge but gets shot down mid-flight. Follow the smoke trail to recover its remains.

·Third Balloon: Head to a nearby shack marked on your map. The balloon is tangled on the roof antenna. Climb the ladder or grapple up, interact with it, and collect the final data set.

Tip: Using weapons with splash or elemental damage can make these fights easier. If you're low on resources, you can farm loot or buy Borderlands 4 Money to restock your ammo and supplies more efficiently.

Step 7: Return to Skeptical Sam

Head back to Sam's camp in Southern Terminus Range. Once you show him the surveyor photos, he'll glance at them, mutter about "government holograms," and then reluctantly admit defeat.

He rewards you with XP, Eridium, cash, and a random weapon drop - plus a custom Vault Hunter skin and ECHO-4 frame.

Flat Kairoser Quest Rewards

·XP: Moderate to High (scales with level)

·Eridium: 75-150

·Weapon: Random (Uncommon-Epic tier)

·Cosmetic Unlocks: Vault Hunter Skin, ECHO-4 Frame

·Cash: 10,000-15,000 Credits

Tips for Completing Flat Kairoser Efficiently

·Use Grapple Routes: The mission involves heavy vertical traversal - bring a fast-recharge Grapple Mod.

·Elemental Loadouts Help: Many enemies here are weak to Cryo and Shock damage.

·Don't Skip Ammo Boxes: The fights between travel points can be long. Stock up when you can.

·Listen to Dialogue: Sam's commentary is some of the funniest writing in Borderlands 4, full of satire and inside jokes.

Final Thoughts

The Flat Kairoser quest in Borderlands 4 is one of the standout side missions in the Terminus Range. It perfectly encapsulates the humor and chaos that define the series - with Skeptical Sam serving as both comic relief and social commentary. While the trek across Kairos can take some time, the unique objectives and hilarious writing make it well worth completing for both the loot and the laughs.