Excavation ∞ and its Covert variant are repeatable, challenge-style Commissions in Duet Night Abyss that center on protecting Lunoxplorer’s field equipment while pushing deeper into hostile zones. One track pays out Coins, the other drops Secret Letters. Once you’ve unlocked them, they’re available permanently, so you can route them into your routine whenever you need currency or specific drops.

Excavation ∞ overview and unlock

Field Details
Main objective Assist Lunoxplorer with terrain excavation and safeguard the Excavators
Commission type Commission
Primary reward Coins
How to unlock Finish Chapter Noctoyager 1: The Art of Survival
Availability Open permanently in Commissions once unlocked

Excavation ∞ tier rewards and requirements

Each difficulty tier has a level gate and either a story, progression, or completion prerequisite. Early tiers award flat Coin bundles:

Commission Level Unique rewards Unlock requirement
Excavation ∞ I Lv. 10 6,300 Coins Finish Chapter Noctoyager 1: The Art of Survival
Excavation ∞ II Lv. 20 9,900 Coins Complete the previous difficulty
Excavation ∞ III Lv. 30 13,500 Coins Reach Trial Lv. 25
Excavation ∞ IV Lv. 40 17,100 Coins Reach Trial Lv. 35
Excavation ∞ V Lv. 50 20,700 Coins Reach Trial Lv. 45

Later tiers raise the bar further and rotate in tougher enemy mixes (see below). Plan your Trial Level progression so you can step up through the ladder without bottlenecking.

Enemies in higher Excavation ∞ tiers

At higher levels, Excavation ∞ leans on fast, aggressive Filthoid variants and ranged Wildswarm units, with elite enemies in the mix. Expect these enemy types in the upper tiers:

Commission Enemy types present
Excavation ∞ VI (Lv. 60) Savage Filthoid, Savage Filthoid II, Veloci Filthoid, Veloci Filthoid II, Guerrilla Filthoid, Guerrilla Filthoid II, Floating Filthoid, Porter Filthoid, Wildswarm's Sword, Wildswarm's Arrow, Battle Maven
Excavation ∞ VII (Lv. 70) Savage Filthoid, Savage Filthoid II, Veloci Filthoid, Veloci Filthoid II, Guerrilla Filthoid, Guerrilla Filthoid II, Floating Filthoid, Porter Filthoid, Wildswarm's Sword, Wildswarm's Arrow, Battle Maven
Tip: These lineups pressure objectives from multiple angles. Keep an eye on ranged Wildswarm units while intercepting high-mobility Filthoids before they reach the Excavators.

Covert Excavation ∞ overview and unlock

Field Details
Main objective Assist Lunoxplorer with terrain excavation and safeguard the Excavators
Commission type Covert Commission
Primary reward Secret Letter Drops
How to unlock Finish the special side quest “Go, Geniemons!”

Covert Excavation ∞ mirrors the core objective but shifts the reward pool to Secret Letters. Use it when you need those drops rather than Coins.

What to focus on when you play

  • Objective-first play: the clear condition hinges on keeping Excavators intact. Position and rotate to the device under threat, not just to enemies.
  • Meet the gates: tier unlocks are tied to Trial Levels (25/35/45 for tiers III–V) and prior clears, so level planning matters.
  • Return any time: once unlocked, both modes stay available in the Commissions list, making them reliable farms for Coins or Secret Letters.

Once Chapter Noctoyager 1 is complete, slot Excavation ∞ into your daily loop for Coins and climb as your Trial Level allows. When you need Secret Letters instead, pivot to the Covert variant after finishing “Go, Geniemons!” Both tracks are permanent fixtures, so you can move between them as your current goals change.