Limbus Company Mirror Dungeon 4: Best Builds and Fusion
Complete Limbus Company Mirror Dungeon guide: 5-floor progression, E.G.O Gift fusion odds, shop restock costs, and optimal keyword team archetypes.
Mirror Dungeon features 5 floors with increasing Cost rewards (75 to 250+). E.G.O Gift keyword fusion yields 60%, 90%, and 99% success rates (up to 99.99% with Wishmaking).
Quick Jump to Mirror Dungeon 4: Floor Progression · Cost Economy · Shop Functions · Gift Fusion Odds · Starlight Rewards · Floor 4 Lunacy
The Mirror Dungeon is the premier roguelike testing ground in Limbus Company. Managers field customized squads across 5 sequential floors, gathering E.G.O Gifts, optimizing Skill decks, and accumulating Sin resources across encounters. Entry into the dungeon is free of charge; claiming final rewards consumes Enkephalin Modules (5 modules for Normal, and 6 per weekly bonus charge for Hard Mode).
Successfully navigating the Mirror Dungeon requires balancing your combat economy (Cost), managing shop upgrades, and targeting synergistic keyword E.G.O Gifts.
5-Floor Progression and Route Strategy
A standard run consists of 5 Floors on both Normal and Hard difficulties. Managing your party health, Sanity (SP), and route choices determines how smoothly your squad scales into late floors.
Floor-by-Floor Breakdown
- Floor 1 (Establishment): Focus on normal encounters to build initial Sin resources and push your core Sinners toward 45 SP. Starting Cost begins at 200 (plus Starlight conversions).
- Floor 2 (Keyword Assembly): Prioritize Risky or Abnormality nodes to collect foundational Tier I and Tier II E.G.O Gifts matching your squad’s primary status keyword (Tremor, Rupture, Sinking, or Bleed).
- Floor 3 (Difficulty Spike): Enemies begin scaling in Clash Power and speed. Use the Floor 3 shop to replace weak Skill 1s with high-power Skill 2s or 3s. Remember that all Sinners are revived and healed upon advancing to a new floor.
- Floor 4 (Resource Consolidation): High-yield encounters offer substantial Cost payouts (150 to 180 Cost). If you are grinding solely for weekly Lunacy, clearing Floor 4 allows you to claim 100% of the Lunacy payout without fighting the Floor 5 boss.
- Floor 5 (Final Boss & Fusion Apex): The culmination of the run. Visit the final shop node directly preceding the Floor Boss to enhance key Tier IV Gifts and execute high-probability Gift fusions.
Cost Economy: Encounter Rewards
Cost serves as the active currency within the dungeon. Each victory rewards Cost based on the encounter classification and chosen difficulty:
| Encounter Type | Normal Difficulty Cost | Hard Difficulty Cost |
|---|---|---|
| Normal Encounter | 75 | 85 |
| Focused Encounter | 100 | 120 |
| Risky Encounter | 120 | 150 |
| Abnormality Focused Encounter | 150 | 180 |
| Floor Boss Encounter | 200+ | 250+ |
Starting Cost begins at a base of 200. Additional starting capital is granted by converting unspent Starlight charges at a 1:5 ratio, alongside any unlocked Starter Buff nodes in the tech tree.
Shop Functions and Costs
Shop nodes appear right before the final Floor Boss on each floor. Efficient spending separates smooth runs from wipeouts.
| Shop Function | Cost | Strategic Application |
|---|---|---|
| Heal Sinner | 100 | Restores 1 Sinner to 50% HP and 45 SP, all Sinners to 15% HP and 15 SP, or revives a fallen ally. |
| Team Reconfiguration | 100 | Swap Identities or E.G.O for up to 3 Sinners for a flat 100 Cost fee. |
| Skill Replacement | 45 / 75 / 120 | Upgrade Skill 1 into Skill 2 (45), Skill 2 into Skill 3 (75), or Skill 1 into Skill 3 (120). |
| Super Shop Search | 90/25, 150/50, 240/75 | Target specific replacement skills in rare Super Shops (appears in Hard Mode). |
| E.G.O Gift Dispenser | 140 - 600 | Purchase up to 4 displayed E.G.O Gifts tailored to floor pools. |
| Catalog Refresh | 15 (+15 each) | Rerolls the shop inventory; increases by 15 Cost per subsequent roll. |
| Keyword Refresh | 90 (+15 each) | Filters shop offerings toward a chosen status archetype. |
| Sell E.G.O Gifts | 50 - 300 back | Refunds 50% of the Gift’s purchase price to free up budget. |
| Enhance Gifts | 50 - 200 | Upgrades Gift potency across two tiers (Tier I: 50/100, Tier II: 60/120, Tier III: 75/150, Tier IV: 100/200). |
| Fuse Gifts | Free | Merges surplus or off-keyword Gifts into higher-tier status assets. |
Warning on Skill Replacement: Converting skills modifies your deck’s Sin affinity balance. Replacing a unit’s sole Gloom or Sloth skill can disable E.G.O Gift passives that require those affinities to trigger.
E.G.O Gift Fusion Probabilities
Interactive Tool: Use our live Mirror Dungeon Gift Fusion Calculator to compute exact sacrifice points, check Standard vs Super Shop tier thresholds, and consult all 59 fixed recipe trees.
Gift fusion is free of Cost at the shop counter. You select a target Keyword Category, and the probability of obtaining a matching Gift scales with the quantity of components sacrificed:
| Fusion Materials | Base Keyword Probability | With Wishmaking (5 Starlight) |
|---|---|---|
| 2 Gifts | 60% | 90% |
| 3 Gifts | 90% | 99% |
| 4+ Gifts | 99% | 99.99% |
Specialized Recipe Fusions
Certain apex E.G.O Gifts cannot be purchased in shops or dropped from combat encounters. They must be forged using predetermined component recipes. If an ordinary fusion at 99% or higher fails, a compensation Gift is automatically generated.
Starlight Generation and Unlocks
Starlight is the persistent progression currency used to unlock permanent Starter Buffs, fund Wishmaking, and utilize Theme Pack Observation:
- Baseline Completion: 60 Starlight per cleared run.
- Floor Clearance: +1 Starlight per floor cleared (up to 5), with Hard Mode adding an extra 4 times the floor number (up to 20 Starlight).
- Rest Bonus: +1 Starlight for every Rest Bonus charge on participating Identities.
- Theme Pack Bonus: +5 Starlight per Refraction Railway Theme Pack cleared.
- Adversity Payout: +15 Starlight per point of Adversity Score at run conclusion.
- New Release Bonus: 300 Starlight when first obtaining a newly released Identity or E.G.O within 2 weeks of debut.
Weekly Rewards and the Floor 4 Strategy
Every Thursday, 3 weekly bonus charges replenish. Hard Mode allows managers to consume all 3 bonus charges simultaneously in a single 5-floor run, multiplying Lunacy, Battle Pass EXP, and Manager EXP yields to save real-world time.
If your roster struggles against the Floor 5 boss or you are farming under tight time constraints, you can forfeit immediately after conquering Floor 4. The game awards 100% of the weekly Lunacy upon clearing Floor 4, making it the most efficient route for pure currency farming.
Frequently Asked Questions
How many floors does a Limbus Company Mirror Dungeon have?
Standard runs feature 5 floors on both Normal and Hard difficulties. Extended challenge modes include Parallel Superposition (up to 10 floors) and Parallel Superposition EXTREME (up to 15 floors).
What are the odds of getting a targeted Keyword from Gift fusion?
Fusing 2 Gifts yields a 60% chance of the chosen Keyword, 3 Gifts yields 90%, and 4 or more Gifts yields 99%. Spending 5 Starlight on Wishmaking boosts these probabilities to 90%, 99%, and 99.99%.
How much Cost do you start a Mirror Dungeon run with?
Managers begin with a base starting Cost of 200, plus extra Cost converted from leftover Starlight charges (1 Starlight per 5 Cost), and additional bonuses from active Starter Buffs.
Can you claim full Lunacy without clearing Floor 5?
Yes. All weekly Lunacy rewards can be acquired upon clearing Floor 4, allowing players running on limited time to skip the Floor 5 boss encounter without sacrificing premium currency.