No.21: XXI

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Debuts in the Inscription of Labyrinth patch. · Rank: A-Rank · Class: Tank · Element: Physical (20%) Dark (80%) 50%


Originally a subject of a Daedalus corporation experiment, she was retrieved during a mission conducted by Kurono. Later, she was transferred to Babylonia's Task Force with Vera. She is gloomy and seemingly expresionless in appearance. However, she becomes exceptionally vicious and dangerous under extreme circumstances.
Burst — A signature move that can deal massive DMG
Forced Evasion — Can remove abnormal status effects when in Haywire status
Physical (20%) Dark (80%)
No. 21
21 Jan
Collab Bot
Audiovisual Terminal

Optimal Weapon: Snore

Wide-Energy Pressure Core: Whenever No. 21: XXI performs Shadow Prism attacks, a QTE, or disrupts incoming enemy attacks, the Co-Bot unleashes a Force Wave that deals 50% AOE Dark DMG to enemies (only triggers once per second).

Energy Suppression Unit: Hitting allies with Force Wave will grant them Energy Suppression for 3s. Energy Suppression: Dark DMG reduces the enemy's healing received by 100% for 3s.

Impulse Fort Module: When the Force Wave detonates 6 Twilight Matrices at once, the Co-Bot enters Fortification mode, unleashing a hyper-pulse that deals Dark DMG equal to 411.76% of No. 21: XXI's ATK (DMG scales with Core Passive level).

Inver-Resonance Unit 2.0: Increases the Extra DMG Bonus of No. 21: XXI's Twilight Matrix and Resonance Pulse by 15%.

Memory Builds ◇ No.21: XXI

A list of recommended builds for No.21: XXI can be found here. Each tab represents one build — click the tabs below to view each one.
See here for more information about Ultima Awakening and resonance slots.

Disclaimer: Memories displayed here are arranged so that their stats are optimized based on their varying values in different positions.
However, it's more cost-effective to arrange all 2-piece sets in top slots for easy swapping between builds, even if stats aren't optimized.

Memory Placement
Bathlon x4 / Einsteina x2
Memory Resonance
Top Resonance Slot (1):
Ex — Tactical Adjustment: HP +75, ATK +15 x6

Bottom Resonance Slot (2):
Tank: Class Skill Level +1 x6
Key Notes
  • No.21: XXI's main build
  • Ultima Awakening Set
  • General-purpose QTE support set
  • Allows XXI to debuff on QTE.
  • Can also be used for DPS on high difficulty stages.

Weapon Resonance ◇ No.21: XXI

Recommended 6★ weapon resonances for No.21: XXI can be found here listed in order of priority.

1. Tenebrion Shock
Inflicts Dark Wave effect upon dealing Dark damage. Dark Wave: reduces the target's Dark resistance by 8% for 8s. Repeated triggering refreshes the duration.
2. Dead Line Timing
Gain 2 extra random signal orbs upon deployment, and 3 signal orbs of the same color every 45s (also gain signal orbs on standby).
3. Resonant Echo
The duration of effect inflicted by Tank class skill increases to 8s.
4. Boundary's Annihilation
On QTE, shields the Construct in control for 10% of the skill user's max HP for 5s.
  • Tenebrion Shock


  • Dead Line Timing
  • Resonant Echo


  • Boundary's Annihilation
Minimum recommended amount: 1
  • Boundary's Annihilation is mainly equipped in Phantom Pain Cage to keep 100% HP for the highest possible score.

Skills & Passives

Red Orb

Nightfall Realm

Red Orb — Ping Red Orb
Automatically uses a 3-Ping version of this attack upon switch-in.
Leaps into the air and expands a Duskglow Realm on the target's location. It pulls enemies in a large area once and then continues pulling the enemies within the realm, deaing Physical DMG (Dark DMG instead on a 3-Ping), and No. 21: XXI will stay in the air briefly, during which an Instant Dodge will release 3 Twiight Matrices on the target's location.
- Deals 100% / 200% / 300% Physical DMG in total based on the number of orbs pinged.

Red Orb — Co-Bot + Ping Red Orb
Co-Bot: When No. 21: XXI releases a Twilight Matrix, it triggers a realm collapse in the Duskglow Realm, pulling enemies in a large area and deaing Dark DMG.
-Deals 60% Dark DMG.
Yellow Orb

Dusk Bladewheel — Ping Yellow Orb

Leaps in the direction of the joystick and releases a Dusk Bladewheel that deals Physical DMG (Dark DMG instead on a 3-Ping), and No. 21: XXI will stay in the air briefly, during which an Instant Dodge will release 3 Twilight Matrices on the target's location.
- Deals 140% / 280% / 420% Physical DMG in total based on the number of orbs pinged.
Blue Orb

Cluster Recursion

Blue Orb — Ping Blue Orb
Enters the Hyperposition state and copies the following Basic Attacks and Shadow Prism Attacks. The effect does not stack.
- Copies the following 1 / 2 / 4 Basic Attacks and Shadow Prism Attacks based on the number of orbs pinged.

Blue Orb — Co-Bot + Ping Blue Orb
Co-Bot: Immediately launches a dash attack at the current target, dealing Physical DMG and reducing the DMG the target deals.
- Deals 40% Physical DMG in total.
- Reduces the DMG the enemy deals bv 20% for 5s. This effect can only be triggered once every 2s.
Basic Attack

Prism Barrage

Basic Attack — Tap Basic Attack
Attacks with laser beams to deal Physical DMG.
- Deals 348% Physical DMG in total.

Basic Attack — Co-Bot + Tap Basic Attack
Co-Bot: Automatically attacks the current target, dealing Physical DMG. The Co-Bot always stays on the field.
- Deals 20% Physical DMG in total.

Shadow Prism Agglomerate

Shadow Prism Attack — Tap Basic Attack consecutively
No. 21: XXI's Basic Attack will generate Shadow Prism Energy. Upon reaching a certain level of Shadow Prism Energy, the next Basic Attack will empty all Shadow Prism Energy to cast a Shadow Prism Attack and create 1 Twilight Matrix on the targets location that deals Dark DMG and knocks the target down. When generated, the Twilight Matrix grants No.21: XXI Signature Energy and Dodge Energy.
- Each Basic Attack generates 1 Shadow Prism Energy. Upon reaching 4 Shadow Prism Energy, Shadow Prism Attack will be unleashed.
- Deals 20% Dark DMG.
- Twilight Matrix lasts 3s. When generated, it grants No.21: XXI 2 Signature Energy and 50 Dodge Energy.

Resonance Pulse — Co-Bot + Twilight Matrix present
When the Co-Bot's Force Wave destroys a Twilight Matrix, it will trigger a Resonance Pulse, dealing Dark DMG to nearby enemies.
- Deals 50% Dark DMG to nearby enemies.

Instant Dodge — Uncontrollable state + Tap Dodge
When No. 21: XXI is uncontrollable (when attacked, downed, or in mid-air), press the Dodge button to perform Instant Dodge with extra Dodge Energy to negate all uncontrollable states and create 1 Twilight Matrix on the target's location. Instant Dodge grants No. 21: XXI Super Armor and Shield.
- Instant Dodge costs 1.2x Dodge Energy (300).
- Instant Dodge grants No. 21: XXI Super Armor for 2s and Shield equal to 15% of max HP.

Shadow Prism Collapse

Signature Move — 120 Energy + Tap Signature + Quickly ping Blue Orb + Quickly tap Basic Attack
Casts an Enhanced Duskglow Realm on the target's location and enters Quick Attack mode. Spends all Signal Orbs and Shadow Prism Energy to get unlimited Blue Orbs and extreme attack speed for 3s. When Quick Attack mode ends, the realm explodes to deal Dark DMG and empty No. 21: XXI's Energy, Blue Orbs and buffs. Creating Twilight Matrices during the Signature Move will increase the explosion's Extra DMG Bonus.
Co-Bot: It will not perform other skills while the Signature Move is being cast. When Quick Attack mode ends, it releases a Force Wave to detonate all Twilight Matrices.
- During Signature Move, every Basic Attack deals 20% Dark DMG.
- The realm explosion deals 600% Dark DMG.
- While casting the Signature Move, creating 1 / 2 / 3 / 4 / 5 Twilight Matrices will increase the explosion's Extra DMG Bonus by 40 / 80 / 120 / 160 / 200%.
- When there are 6 Twilight Matrices, the Signature Move will achieve an S Rank, increasing the explosion DMG by 300%.

Signature Move — Co-Bot + Signature active
Co-Bot: It will not perform other skills while the Signature Move is being cast. When Quick Attack mode ends, it releases a Force Wave to detonate all Twilight Matrices.

Twilight Shackles

Expands a Duskglow Realm on the target's location to deal Dark DMG, creates 3 Twilight Matrices, and triggers a realm collapse.
- Deals 200% Dark DMG.

Faded Camouflage

Dodge Gauge limit and Extra DMG Bonus of team members increase by 250 and 5% respectively.


Attacks reduce the target's Extra DMG Reduction by 20% for 5s.

Ultima Awaken

Gains 3 Signal Orbs when entering battle.


When No. 21: XXI has Shield, her Extra DMG Bonus increases by 5%. If not, her Extra DMG Reduction increases by 10%. A Blue 3-Ping will fully restore Shadow Prism Energy (inactive when performing her Signature Move).


When creating a Twilight Matrix, grants allies on the field 20% Extra DMG Reduction and 25% Extra Dodge Gauge Recovery Speed for 2s. This effect can stack up to 3 times. The duration will not reset when it is re-triggered. Enemies in the Duskglow Realm will be afflicted with Chain Fusion (Dark Resistance decreases by 10%) for 5s.
SSS+ Rank


When her Signature Move achieves an S rank, the Extra DMG Bonus of the explosion from Duskglow Realm increases by 210%. The Co-Bots attacks will grant all allies on the field Shield equal to 2% (stacking up to 10%) of No. 21: XXI's max HP.

How to play

XXI - Fundamentals
  • While XXI is in midair immediately after a Red Orb 3-Ping or a Yellow Orb 3-Ping, perform an Instant Dodge to drop 3 Twilight Matrices on-field
    • Each Twilight Matrix dropped will deal damage to enemies and restore 50 Dodge Energy to XXI
  • Trigger Resonance Pulses with the Co-Bot to detonate on-field Twilight Matrices to deal additional damage
    • Perform Basic Attacks in conjunction with Blue Orb Pings to generate Shadow Prism Energy
    • Once XXI has 4 Shadow Prism Energy, the next Basic Attack will launch a Shadow Prism Attack, drop 1 Twilight Matrix on-field, and cause the Co-Bot to release a Resonance Pulse and detonate on-field Twilight Matrices
    • Twilight Matrices that are not detonated within 4 seconds of being placed on-field will vanish without dealing damage (matrices last 3 seconds and take 1 second to completely disappear)
  • While XXI is being attacked or knocked down, she can perform an Instant Dodge to drop 1 Twilight Matrix on-field and allow her to escape from hitstun
  • After casting XXI's Signature Move, alternate between performing 1 Blue Orb 3-Ping and 2 Basic Attacks to achieve an S-Rank rating and deal maximum damage
XXI - Additional Information
  • Basic Attacks only need to be cast to generate Shadow Prism Energy, they do not need to hit a target
  • Blue Orb Pings will duplicate a set number of the next Basic Attacks performed, doubling the amount of Shadow Prism Energy gained from those attacks and causing affected Shadow Prism Attacks to drop 2 Twilight Matrices
  • Holding a direction while casting Yellow Orb Pings will move XXI in the held direction during the skill cast
  • Because XXI's Signature Move clears away all of her existing orbs, it is only recommended to cast it when XXI is low on orbs or in emergencies when XXI is out of Dodge Energy and in danger of dying
  • Instant Dodges give XXI a 15% max HP shield, grant 2 seconds of Super Armor, and cost 300 Dodge Energy (slightly more than the 250 a normal Dodge costs)
    • This extra cost is generally offset by the Dodge Energy restored by the Twilight Matrices dropped immediately afterwards
    • Instant Dodges are still Dodges, meaning they can be used to dodge attacks and trigger Matrix just like an ordinary Dodge
    • Casting a Red Orb 3-Ping or Yellow Orb 3-Ping just before an enemy attack, and then timing the subsequent Instant Dodge to dodge that attack, allows XXI to dodge attacks while both dealing damage and expending essentially zero Dodge Energy
  • When XXI's Dodge Gauge is completely drained, dropped Twilight Matrices will not grant Dodge Energy until XXI's natural Dodge Energy regeneration restarts
    • If XXI gets knocked down in challenge content and is low on Dodge Energy, it may be wiser to wait out the knockdown invulnerability to allow her Dodge Energy to regenerate, since XXI's damage output is dependent on maintaining a healthy Dodge Gauge to Instant Dodge with after Red Orb 3-Pings and Yellow Orb 3-Pings
  • XXI's Co-Bot remains on-field and attacks with the on-field character, allowing XXI to debuff enemies with her Tank Class passive even while XXI is off-field
    • The Co-Bot will remain on-field performing attacks even if XXI dies, however it will no longer apply the Tank Class passive if she is dead


Related Frames

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