Honkai: Star Rail Mortenax Blade Build Guide — Best Light Cones, Relics, Teams & Rotation (Version 4.3)

Mortenax Blade Overview — Who Is He?

Mortenax Blade is a 5-star Fire Nihility character introduced in Honkai: Star Rail Version 4.3 (June 2026). He is the evolved form of the original Blade, now serving as one of the most versatile and powerful units in the entire game. According to Prydwen's tier list, he earns a T0 rating across all three endgame modes — Memory of Chaos, Pure Fiction, and Apocalyptic Shadow.

What makes Mortenax Blade unique is his triple identity: he functions as a universal support, a sub-DPS, and even a competitive hypercarry all in one package. His entire kit scales off Max HP, making him extremely tanky while dealing massive damage.

Core Mechanic: Infinite Fury State

Blade's gameplay revolves around his Ultimate "Fornax Ex Corpore", which activates the Infinite Fury state. While active, he gains massive stat boosts, unlocks a free SP-costless Skill, and cannot die. If he takes a killing blow, he simply dispels his Zone and restores 50% HP instead.

Role	Team Fit	Endgame Rating
Universal Support	Any team composition	T0 (MoC/PF/AS)
Sub-DPS	Dual carry setups	T0
Hypercarry	Dedicated DPS team	T0.5

Infinite Fury Buff	Value
Bonus CRIT Rate	+20%
Bonus CRIT DMG	+60%
Skill SP Cost	0 (Free)
Damage Reduction	+50% (via A4)
Death Prevention	Defy death once per Zone

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Best Light Cones for Mortenax Blade

Choosing the right Light Cone is critical for maximizing Mortenax Blade's potential. His signature cone, Reforged in Hellfire, is his best-in-slot by a noticeable margin, but there are strong alternatives for F2P players.

Light Cone Tier List

Rank	Light Cone	DPS% vs Base	Key Effect	EHR Required
#1	Reforged in Hellfire (S1)	117%	Max HP +30%, 20 Energy per wave, "Purgatory" debuff (+30% CRIT DMG taken)	0%
#2	Lies Dance on the Breeze (S1)	112%	18% SPD, 24% DEF Reduction debuff	40%
#3	Resolution Shines As Pearls of Sweat (S5)	100%	16% DEF Reduction debuff (4★)	67%
#4	Holiday Thermae Escapade (S5)	96%	16% Vulnerability debuff (Battle Pass)	67%
#5	Before the Tutorial Mission Starts (S5)	95%	40% EHR, Energy on hit (Free, Mission Reward)	0%

Why Reforged in Hellfire Is the Best

Reforged in Hellfire (S1) Effect:
• Increases Max HP by 30%
• Regenerates 20 Energy at the start of each wave
• After Skill Attack, inflicts "Purgatory" for 2 turns
• Enemies in "Purgatory" take +30% CRIT DMG (stacking to +60% from Blade)

The 30% HP boost perfectly synergizes with Blade's HP-scaling damage. The 20 Energy injection guarantees a first-turn Ultimate, which is crucial for activating Infinite Fury immediately. And the Purgatory debuff provides massive team-wide CRIT DMG amplification that benefits the entire squad.

For F2P players, Resolution Shines As Pearls of Sweat (S5) or Before the Tutorial Mission Starts (S5) are excellent alternatives. As noted by Icy Veins' comprehensive analysis, these options provide solid debuff support even without spending on the gacha.

Best Relics & Planar Ornaments

Best Relic Sets

Rank	Set	2-Piece Bonus	4-Piece Bonus	Usage Rate
#1	Divine-Querying Master Smith	Max HP +12%	CRIT DMG +28% vs DEF-reduced enemies + 15% team DMG buff	79%
#2	Pioneer Diver of Dead Waters	DMG +12% vs debuffed enemies	CRIT Rate +4%, scaling CRIT DMG per debuff	8%
#3	Longevous Disciple	Max HP +12%	CRIT Rate +8% per stack (max 2) on HP loss	1%

Best Planar Ornaments

Rank	Set	2-Piece Bonus	Requirement
#1	Bone Collection's Serene Demesne	Max HP +12%; CRIT DMG +28%	HP ≥ 5,000
#2	Sprightly Vonwacq	Energy Regen +5%; 40% action advance	First-turn Ultimate setup
#3	Inert Salsotto	CRIT Rate +8%; Ultimate/FUA DMG +15%	CRIT Rate ≥ 50%

Recommended Build: Divine-Querying Master Smith (4-PC) + Bone Collection's Serene Demesne (2-PC)

This combination is used by 79% of top players (per Prydwen's statistics) because it maximizes both Mortenax Blade's personal damage output and his team support capabilities. The 4-piece set's CRIT DMG bonus triggers off his own Ultimate's DEF Reduction, ensuring near-permanent uptime, while the team-wide 15% DMG buff increases overall squad DPS.

If you're prioritizing Mortenax Blade as a pure support for Acheron or another carry, consider swapping to Sprightly Vonwacq for faster first-turn Ultimate activation.

Stat Priority & Endgame Stats

Building Mortenax Blade is straightforward since he scales entirely off HP. Here are the stat targets you should aim for:

Main Stat Priority

Gear Slot	Primary Stat	Alternative
Body	CRIT Rate	Effect Hit Rate (if LC requires it)
Feet	SPD	HP%
Planar Sphere	HP%	Fire DMG%
Link Rope	Energy Regen Rate	HP%

Important Note: Never build ATK% on Mortenax Blade. Every single damage multiplier in his kit uses Max HP, making ATK completely wasted.

Endgame Stat Targets

Stat	Minimum Target	Ideal Target
HP	6,000	6,500+
SPD	134	160 (or 170 for specific builds)
CRIT Rate	80%	100% (in-combat, after Ultimate's +20%)
CRIT DMG	130%	160-220%
Effect Hit Rate	0% or threshold	Depends on Light Cone choice

Substats Priority Order

CRIT Rate = CRIT DMG > SPD > HP% > Effect Hit Rate (to threshold)

Substats Note: For pure support builds, SPD can be prioritized over CRIT stats since your primary job is debuff application uptime rather than personal damage.

Best Teams for Mortenax Blade

Mortenax Blade fits into an extraordinary range of team compositions. According to Icy Veins' team analysis, his most powerful setups involve frequent attackers who can both feed his Talent Charges and benefit from his debuffs.

Top 3 Team Compositions

Team	DPS	Amplifier	Flex	Sustain
Acheron Premium	Acheron	Mortenax Blade	Tribbie / Ashveil / Cipher	Hyacine / Dan Heng PT
FUA Dual Carry	Ashveil	Mortenax Blade	Tribbie	Hyacine
Hypercarry Blade	Mortenax Blade	Bronya / Ruan Mei	Tribbie / Pela	Hyacine / Fu Xuan

Team 1: Acheron Premium (T0)

Mortenax Blade is currently Acheron's strongest Nihility partner — hands down. Here's why:

Every ally attack under Blade's Zone applies a debuff, generating Slashed Dream stacks for Acheron
Enemies attacking Blade also trigger debuff application via his A4 Trace
His Ultimate provides 30% DEF Reduction + 50% Vulnerability — two of the strongest debuffs in the game
His A6 Trace boosts team Ultimate DMG by an additional 75% (with a second Nihility)

The result? Acheron gets her Ultimate faster and hits harder than with any other support option.

Team 2: Follow-up ATK Dual Carry (T0)

Mortenax Blade + Ashveil forms one of the most devastating dual-carry duos in the game:

Ashveil's attacks charge Mortenax Blade's Talent (giving him Follow-up Skills)
Blade's attacks hit "The Bait," generating Energy for Ashveil
Together, they reach 70% DEF Reduction on enemies
Blade provides 50% team DMG buff; Ashveil provides CRIT DMG buffs

Team 3: Hypercarry Mortenax Blade

If you want Blade to be the main damage dealer, pair him with:

Bronya for action advance and DMG buffs
Tribbie or Pela for additional debuffs
Hyacine for Max HP buffs (which directly increase Blade's damage)

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Rotation & Gameplay Tips

Basic Combat Rotation

Battle Start: Use Technique → Taunts all enemies + 90% DMG reduction for 2 turns
Turn 1: Cast Ultimate → Activate Infinite Fury state, apply Balefire Bind (DEF Reduction + Vulnerability)
Infinite Fury: Spam Skill — it costs 0 SP, deals massive AoE damage, and bounces additional hits
Talent Procs: At 9 Charges, automatically use Skill as a Follow-up ATK (+25 extra Energy)
Maintain: When Infinite Fury ends (countdown reaches 0), use A2's Energy overflow to instantly recast Ultimate
Repeat: Keep the cycle going for near-permanent Infinite Fury uptime

Advanced Tips

1. Energy Management Is Everything Blade's A2 Trace allows Energy overflow up to 80 points. After his Ultimate, this overflow is refunded, meaning you should never let Energy cap without using it. An Energy Regen Rope is highly recommended for longer encounters.

2. Use Basic ATK's Taunt Strategically His Basic ATK applies a 100% guaranteed forced Taunt — no Effect Hit Rate check needed. Use this to redirect dangerous boss attacks away from squishy teammates.

3. Learn the Charge Economy

Ally attacks → 1 Charge
Blade getting hit → 1 Charge (via A4)
Need 9 Charges for a Follow-up Skill proc
At E2: Cap reduces to 7 Charges, meaning faster Follow-ups

4. Survival Is Automatic Blade has exceptional built-in survivability:

HP-scaling makes him naturally tanky
A4 gives 50% DMG Reduction + 50% Incoming Healing
Technique gives 90% DMG Reduction for 2 turns
Infinite Fury prevents death once per activation

Common Mistakes to Avoid

Mistake	Why It Hurts	Correct Approach
Building ATK%	Blade's damage scales entirely off HP	Use HP% on all main stats
Ignoring EHR	Debuff Light Cones won't proc reliably	Check your LC's EHR threshold
Using Skill outside Fury	Skill is locked without Infinite Fury	Always activate Ultimate first
Skipping Energy Rope	Longer downtime between Fury states	Use Energy Regen Rope for better uptime
Forgetting the Taunt	Misses a powerful control tool	Basic ATK Taunt is 100% guaranteed

Eidolon Guide — Which Ones Are Worth It?

Mortenax Blade is fully functional at E0 and already one of the strongest units in the game. However, his Eidolons offer substantial power spikes if you're considering vertical investment.

Eidolon Power Breakdown

Eidolon	Effect	Power Gain vs E0	Verdict
E1	20% All-Type RES shred; Countdown delay on FUA Skill	+16%	✅ Strong support upgrade
E2	Allies' Ultimates = FUA; FUA DMG +75%; Charge cap → 7	+55%	⭐ Best stopping point
E3	Ultimate/Talent +2 levels	+7%	❌ Skip
E4	A6: additional +50% ally DMG	+33%	🔶 Niche
E5	Skill/Basic ATK level increase	+1%	❌ Skip
E6	Charge on HP loss; Enhanced Ultimate 1.5x multiplier	+46%	💎 Whale territory

Recommendation by Investment Level

E0 (F2P / Low Spender): Already a T0 unit in all endgame modes. Save your resources for other characters.

E1 (Mid Spender): The 20% All-Type RES shred is a universal buff that benefits the entire team. The countdown delay improves Infinite Fury uptime.

E2 (High Spender): Best stopping point. This changes the game — allies' Ultimates count as Follow-up attacks, enabling synergies with Ashveil and other FUA-focused characters. Combined with Charge cap reduction to 7, Blade's rotation speed increases dramatically.

E6 (Whale): If you can afford it, the 1.5x multiplier on his Enhanced Ultimate combined with Charge-on-HP-loss turns Blade into an absolute monster.

Final Verdict

Mortenax Blade is unquestionably one of the strongest single units in Honkai: Star Rail as of Version 4.3. His ability to function as a universal support, debuff machine, sub-DPS, and even hypercarry makes him an incredibly versatile addition to any account.

Content	Rating	Why
Memory of Chaos	T0	Endless debuffs, massive team buffs, strong personal damage
Pure Fiction	T0	AoE damage + Follow-up procs clear waves efficiently
Apocalyptic Shadow	T0	Taunt control + DEF shred + Vulnerability dominate single targets

Should you pull? If you have Acheron, the answer is a resounding yes — he's her best-in-slot teammate by a wide margin. Even without Acheron, his universal utility and competitive personal damage make him a must-have for any account looking to dominate all three endgame modes.

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