Defense Construction is an Exploration Mission in Arknights: Endfield that teaches you how to build and power automated defenses for your outpost. The quest takes place in Valley Pass within the Valley IV region and rewards 75 Oroberyl plus 300 Operational EXP upon completion.
Quick answer: Complete the Fort Showdown main mission to unlock Defense Construction, then place Combat Facilities powered by an Electric Pylon near the outpost entrance to defeat two waves of Landbreakers—21 manually and another wave via Auto-Battle.
Unlock requirements
Defense Construction becomes available automatically after you finish the Fort Showdown main mission. You cannot access this quest earlier in the story progression, so focus on completing the main campaign through Fort Showdown first if the mission hasn't appeared in your quest log.
Talk to Daniel at Valley Pass Outpost
Step 1: Travel to the Valley Pass Outpost and locate Daniel. Speak with him to learn about the current situation at the camp.
Step 2: During the conversation, a camp member named Dewey interrupts with urgent news about an incoming Landbreaker attack. This triggers the first combat phase.
Defeat the initial Landbreaker wave
Step 1: Engage the Landbreakers that have broken into the camp. You need to eliminate all enemies in this encounter to proceed.
Step 2: After clearing the enemies, return to the Temporary Shelter and speak with Daniel again. He'll be standing next to Soth, and this conversation sets up the outpost defense preparation.
Set up Combat Facilities around the outpost
The core mechanic of this quest involves placing Combat Facilities—automated turrets that attack enemies within range. These structures require power from an Electric Pylon to function.
Step 1: Open your AIC building menu and select Combat Facilities, such as Gun Towers. Place them around the Valley Pass outpost, positioning them near the entrance where enemies will approach.
Step 2: Deploy an Electric Pylon within range of your Combat Facilities. All turrets must fall within the pylon's power radius to operate. A box formation with four Combat Facilities surrounding the pylon works well for coverage.
Step 3: Connect power from your Sub-PAC to the Electric Pylon by initiating transmission at the PAC and then plugging the transmission cable at the pylon location.
Defeat 21 Landbreakers in the manual battle
Step 1: Start the battle once your defenses are ready. Enemies will approach the outpost in waves.
Step 2: Let your Combat Facilities engage the Landbreakers automatically. You can also participate directly in combat to speed up the process. The objective requires eliminating exactly 21 Landbreakers before this phase ends.
Complete the Auto-Defense phase
After the manual battle, the quest introduces Auto-Battle mode where your Combat Facilities must handle enemies without your direct intervention.
Step 1: Add more Combat Facilities if needed to strengthen your defenses. Ensure all structures remain within the Electric Pylon's power range.
Step 2: Initiate the Auto-Battle. During this phase, you cannot fight alongside your turrets—the automated defenses must eliminate all incoming enemies on their own. If your setup from the previous phase was solid, the turrets should handle this wave without difficulty.
Check the Early Warning Terminal
Step 1: Once the Auto-Battle concludes successfully, locate the Early Warning Terminal at the outpost. Interact with it to view the current defense status.
Step 2: The terminal displays outpost metrics and tracks milestones that reward you as you progress. This feature remains accessible after the quest ends, allowing you to monitor defense performance and claim additional rewards over time.
Finish the quest with Daniel
Step 1: Return to Daniel at the outpost for a final conversation about the camp's improved security situation.
Step 2: After the dialogue ends, the mission completes. You receive 75 Oroberyl and 300 Operational EXP, and the Early Warning Terminal becomes permanently unlocked for future use.
Combat Facility placement tips
Positioning matters more than quantity. Place turrets where they have clear sightlines to the entrance paths enemies use. Stacking all facilities in one spot creates overlapping fire zones but leaves flanks exposed if enemies approach from multiple directions.
The Electric Pylon has a limited radius, so plan your layout before placing structures. Moving facilities after placement wastes resources and time. If you're unsure about coverage, start with a compact diamond or square pattern around the pylon and expand outward as needed.
Defense Construction serves as a practical introduction to Arknights: Endfield's automated base defense systems. The Early Warning Terminal you unlock here becomes increasingly useful as you expand operations across Valley IV, providing ongoing rewards and strategic information about incoming threats to your outposts.
