HSR 4.3 The Lethe Below the Living — Complete Patch Breakdown Guide

HSR 4.3 "The Lethe Below the Living" — The Full Patch Breakdown

Patch 4.3 lands June 1, and it's carrying serious weight. The Planarcadia storyline reaches its finale, and the big story hook is Blade — his fate in Elio's script is literally left blank. That ambiguity is narrative dynamite for a character who's been at the center of the Stellaron Hunter arc since launch. But beyond the story beats, 4.3 delivers a genuinely important meta unit in Mortenax Blade, the game's first Trailblazer outfit, and a banner schedule that forces hard choices.

This is a patch where what you pull matters. There's one new 5★, three rerun banners, and a signature Light Cone competing for your Stellar Jade. If you're budgeting pulls or trying to figure out whether Mortenax Blade is worth your savings, this breakdown covers the kit, the teams, the relic farm, and the banner order so you can make that call before maintenance ends. Run your numbers through our gacha budget calculator and check your pity tracker before you commit.

What's in 4.3 — The 60-Second Version

If you only have a minute, here's everything arriving in 4.3 in one scannable list:

• New 5★ character: Mortenax Blade — Fire Nihility debuffer. Deploys a Bounded Field from his Ultimate that applies DEF shred, vulnerability, and CRIT DMG amplification to enemies inside it. Built for Acheron teams and follow-up attack archetypes.
• New story chapter: Planarcadia Finale — The conclusion to the Planarcadia arc, with Blade's unresolved fate as the central narrative hook.
• First-ever Trailblazer outfit — "Karmic Fire of the Distant Shore." Unlocked via the Gift of Tempered Blade event, which requires obtaining Mortenax Blade.
• Two new Cavern Relic sets — "Divine-Querying Master Smith" (DEF-shred synergy) and "As Navigator Isee Sees It" (skill/ult DMG amplification).
• Banner Phase 1 (June 1–24): Mortenax Blade (new) + Yao Guang rerun. Featured 4★s: Sampo, Tingyun, Luka.
• Banner Phase 2 (June 24–July 14): Cyrene + Phainon rerun. Featured 4★s: March 7th, Arlan, Yukong.
• Six events running through the patch — Gift of Odyssey (7-day login), Pixel Plane Rumble, Wispae Amusement Park, Gift of Tempered Blade, Planar Fissure, and Realm of the Strange.
• Endgame update: Starward Mode — harder stage tier requiring three fully built teams.
• Quality-of-life updates — including adjustments to the character building experience and relic filtering improvements.

That's a dense patch. The headline item is obviously Mortenax Blade — he's the only new 5★, and his kit has generated more theorycrafting discussion than any unit in the last two patches. Let's get into why.

Mortenax Blade — Kit Breakdown and Why Reddit Can't Agree

Mortenax Blade is a Fire Nihility character, and his entire identity is built around being a premium debuffer. He doesn't deal meaningful personal damage. Every part of his kit funnels into making your damage dealers hit harder, and the way he does it is layered enough that the community is still arguing about his ceiling. Here's the actual mechanic chain:

The Ultimate deploys a Bounded Field. This is the centerpiece. When Mortenax Blade uses his Ultimate, he places a persistent field on the enemy team. Enemies inside the field take increased damage — specifically, they're afflicted with a vulnerability debuff that amplifies all incoming damage, and the field itself provides a DEF shred that lowers their effective defense. This is the foundation everything else builds on.

The Charge system drives the loop. While the Bounded Field is active, every time an ally attacks an enemy inside it, two things happen: the enemy receives an additional stack of debuff amplification, and Mortenax Blade gains a Charge. This creates a feedback loop — the more your team attacks, the more Charges he accumulates, and the more debuffed the enemies become. Follow-up attack teams that hit frequently per turn generate Charges at a much faster rate than slow hypercarry setups.

Full Charge triggers an automatic Skill. When his Charge meter maxes out, Mortenax Blade automatically fires his Skill at no Action Point cost, dealing damage and granting him bonus Energy. This is important because it means he's energy-positive — the auto-Skill refunds enough energy to accelerate his next Ultimate, tightening the uptime on the Bounded Field. In practice, a well-tuned team can keep the field active for the majority of a fight.

CRIT DMG amplification on marked targets. His enhanced state — the Sword Formation — applies a CRIT DMG increase buff to allies attacking enemies within the Bounded Field. This is what pushes him from "good debuffer" to "premium amplifier." DEF shred, vulnerability, and CRIT DMG amp are three distinct multiplicative-ish damage buckets, and stacking all three on the same targets is what makes his ceilings absurd in the right teams.

The community debate. Browse r/HonkaiStarRail or r/HonkaiStarRail_leaks and the discourse splits into two camps. One side calls him the strongest damage amplifier currently in the game, pointing to Acheron team calcs where his DEF shred and CRIT DMG amp push her burst windows into territory that rivals or exceeds dedicated hypercarry supports. The other side argues his narrowness holds him back — he's not a generalist like Ruan Mei or Robin, and if you don't play Acheron or a heavy FuA comp, his value drops significantly. Both positions have merit. He is not a universal pick. He is a premium enabler for two specific archetypes, and within those archetypes, he's arguably the best in slot.

Signature Light Cone (S1) verdict: skip unless you're whaling. His signature Light Cone, "Reforged in Hellfire," provides HP%, energy regeneration rate, and an enhanced CRIT DMG buff to marked targets. The numbers are solid, and the energy regen helps with Bounded Field uptime. But here's the reality: in most of his best teams, the amp value is already saturated by his base kit. The Light Cone adds incremental gains, not a structural change to how he functions. F2P and low-spender accounts should pass — there are serviceable alternatives that get you 80–85% of the value at zero premium cost. If you're a spender with jades to spare and you're committed to an Acheron team long-term, it's a luxury pull, not a priority one.

Banner Pull Priority — What to Skip and What to Whale For

4.3 has a deceptively loaded banner schedule. One new unit and three reruns across two phases means most accounts will have to skip something. Here's how to prioritize.

Phase 1 (June 1–24): Mortenax Blade + Yao Guang, with 4★ Sampo / Tingyun / Luka on rate-up.

Mortenax Blade is the only new unit this patch and the headline pull. If you play Acheron or any follow-up attack team, he's a high-priority target — the amp value he provides isn't replicated by any existing unit. If you don't play either of those archetypes, skip him without hesitation. He's too narrow to justify as a flex pick. The 4★ lineup here is decent: Tingyun is always valuable for energy generation, and Sampo has niche DoT synergy. Luka is the weaker of the three unless you specifically need his single-target DoT application.

Phase 2 (June 24–July 14): Cyrene + Phainon, with 4★ March 7th / Arlan / Yukong on rate-up.

Cyrene is a limited rerun, and if you missed her, this is your window. She's a strong pick for accounts that need her specific archetype — whether she's worth pulling over saving for future patches depends entirely on whether you already have her role covered. Phainon's rerun is lower priority for most accounts; he's solid but not essential, and unless you specifically need his kit, your jades are better spent elsewhere. The 4★ lineup in Phase 2 is weaker: March 7th is easily available and her preservation kit is niche, Arlan is generally considered a low-tier DPS, and Yukong is a usable but awkward buffer with speed-tuning requirements.

Pull priority by account type:

• F2P: Mortenax Blade if you run Acheron. Otherwise save. This is not a patch to spread your limited jades across multiple banners. Pick one target and commit. Use the gacha budget calculator to confirm you can hit pity before the banner ends.
• Low-spenders (monthly pass / battle pass): Mortenax Blade + Cyrene if you can afford both. Skip Phainon unless you're collecting. Skip all signature Light Cones this patch — none are worth the premium cost for their marginal gains. Compare your options with our build comparison tool.
• Veterans / completionists: Priority order is Mortenax Blade (if missing) → Cyrene (if missing) → Phainon (only if collecting). If you already have Cyrene and Phainon, this is a great patch to bank jades for future content.

The bottom line: Phase 1 is where most accounts should focus. Mortenax Blade is the only unit this patch that meaningfully changes team building for the archetypes he supports. Everything else is either a rerun you may already have or a 4★ you can get from any future banner.

Best Teams for Mortenax Blade — Acheron, FuA, and F2P Options

Mortenax Blade is not a generalist. His kit is tuned for two specific team archetypes, and forcing him into anything else wastes his potential. Here are the three builds that actually work.

1. Acheron Hypercarry — His best home by a wide margin.

Full team: Acheron / Mortenax Blade / Pela / Aventurine (or Gallagher/Huohuo). This is the team the community has converged on, and for good reason. Acheron's damage is entirely loaded into her Ultimate burst windows, and Mortenax Blade's layered debuffs — DEF shred, vulnerability, and CRIT DMG amplification — all stack multiplicatively into those windows. His auto-Skill proc generates additional debuff applications that help charge Acheron's Ultimate faster through her Nihility synergy requirements. Pela provides additional DEF shred and ultimate cycling. The sustain slot is flexible: Aventurine for shields and crit synergy, Gallagher for break teams, or Huohuo if you need the energy and cleanse. This team's damage ceiling is among the highest currently available, and Mortenax Blade is the reason it functions.

2. Follow-Up Attack Team with Ashveil — The high-frequency charge engine.

Full team: Ashveil / Mortenax Blade / Topaz (or Jade) / sustain. The logic here is simple: Mortenax Blade's Charge system scales with attack frequency, and follow-up attack comps hit the most times per cycle. Every Topaz proof stack, every Ashveil proc, every FuA trigger feeds a Charge into Mortenax Blade's meter, which means more auto-Skills, more energy, and tighter Bounded Field uptime. The CRIT DMG amplification from his Sword Formation applies to all those follow-up hits, turning a flood of small attacks into a flood of buffed small attacks. This team is less bursty than the Acheron variant but more consistent over long fights.

3. F2P Budget — Functional, not optimal.

Full team: Serval / Mortenax Blade / Pela / Natasha (or Lynx). Serval provides multi-target damage that triggers Charges reasonably well. Pela remains the best F2P DEF-shred option and stacks with Mortenax Blade's own DEF shred. The sustain slot is whatever you have built — Natasha for survival, Lynx if you need cleanse. This team works for clearing story content and most event challenges, but it won't push the hardest Pure Fiction or endgame stages. If you're F2P and pulled Mortenax Blade for an Acheron team, invest your resources there — the budget build exists as a fallback, not a destination.

What does NOT work: Hypercarry comps where only one character attacks per turn (he won't generate enough Charges). DoT teams — his debuffs don't interact meaningfully with damage-over-time mechanics, and the Charge system doesn't proc off DoT ticks. Break teams — while his DEF shred technically helps break damage, the rest of his kit doesn't synergize with the break mechanic loop. If you're not running Acheron or FuA, Mortenax Blade is the wrong unit for the job.

New Relics, Light Cones, and Farm Priorities

4.3 introduces two new Cavern Relic sets, and both are worth understanding even if you don't farm them immediately.

Divine-Querying Master Smith — Mortenax Blade's signature set. The 2-piece provides HP%, and the 4-piece increases damage dealt to enemies with reduced DEF and grants a team-wide buff when DEF shred is applied. This set is explicitly designed for Mortenax Blade — his Bounded Field applies continuous DEF shred, which means the 4-piece team buff is effectively always active in his teams. For him specifically, this is his best-in-slot relic set. Compared to running a generic Nihility set like Prisoner in Deep Confinement, the 4-piece team buff on Divine-Querying Master Smith adds meaningful team damage that the prisoner set's DEF ignore cannot match in sustained encounters.

As Navigator Isee Sees It — A future-facing ATK% set. The 2-piece provides ATK%, and the 4-piece builds skill and ultimate DMG stacks over the course of a fight. This set isn't designed for Mortenax Blade — it's an offensive set that benefits characters who deal significant skill and ultimate damage. It's likely tuned for upcoming DPS releases rather than current meta units. If you're farming relics this patch, this set is lower priority unless you're pre-farming for a leaked future character who can use it.

Farm priority recommendation: Divine-Querying Master Smith is the only set from this patch that's immediately relevant to current meta teams. If you pulled Mortenax Blade, farm his set — the team buff on the 4-piece is worth the investment. If you skipped him, you can safely deprioritize both new sets and continue farming your existing BiS sets.

Signature Light Cone: "Reforged in Hellfire." HP%, energy regeneration rate, and enhanced CRIT DMG buff to marked targets. As discussed in the kit section, this is a solid Light Cone but a low-priority pull. The energy regen helps Bounded Field uptime, and the CRIT DMG buff is additive on top of his kit's base value. For F2P alternatives, "We Will Meet Again" and "Fermata" are serviceable Nihility options that provide debuff utility without the premium cost. Neither matches the signature's CRIT DMG amplification, but both get you most of the way there for zero jades spent.

Events, Endgame Updates, and the Trailblazer Outfit

4.3 runs six events across the patch cycle. Here's what each one offers and what you need to do.

Gift of Odyssey (7-day login event). Log in for seven days during the event period to receive Stellar Jade, credits, and refinement materials. This is free premium currency for minimal effort — do not miss it.

Pixel Plane Rumble. A casual mini-game event featuring a pixel-art aerial racing challenge. Completing stages rewards Stellar Jade, travel encounters, and event-exclusive currency. Low effort, solid rewards.

Wispae Amusement Park. A tower-defense-style event, thematically a spiritual successor to earlier War of the Ephemerals content. Build defenses and clear waves across multiple stages. Rewards include Stellar Jade and upgrade materials. Moderate time investment but straightforward to complete.

Gift of Tempered Blade — the Trailblazer outfit. This event grants the first-ever Trailblazer outfit, "Karmic Fire of the Distant Shore." Important clarification: this outfit is not free. You must obtain Mortenax Blade to unlock it. If you do not pull Mortenax Blade from the Phase 1 banner, you cannot get this outfit. The event itself presents the outfit unlock as a reward, but the prerequisite is owning the character. If you're an outfit collector, this is an additional reason to consider pulling in Phase 1.

Planar Fissure. Double drop event for Planar Ornaments from the Simulated Universe. If you're farming Ornament Extraction for any team, this is the time to spend your Trailblaze Power. Prioritize sets your active teams need.

Realm of the Strange. Double drop event for Cavern Relics. Run this alongside your Divine-Querying Master Smith farm if you pulled Mortenax Blade, or stockpile relics for any character you're building.

Endgame update: Starward Mode. The Starward Mode endgame content receives a new, harder stage tier that requires three fully built, functional teams to clear. This is the game's hardest challenge content to date and a real DPS check for account investment. If you're missing Mortenax Blade's Acheron team archetype or a second strong team comp, this stage will expose that gap. The rewards include premium currency and exclusive upgrade materials. If your account can only field two strong teams, this is a signal to invest in team-building depth before attempting it.

Conclusion — Pull Priority TL;DR

4.3 is a patch with one essential pull decision and a lot of optional ones. Here's the short version:

• If you play Acheron: Pull Mortenax Blade in Phase 1. He's the best amplifier for that team archetype currently in the game, and skipping him leaves significant damage on the table.
• If you play FuA comps: Pull Mortenax Blade in Phase 1. His Charge system and CRIT DMG amplification are tailor-made for high-attack-frequency teams.
• If you play neither: Skip Phase 1 entirely. Save your jades for future patches. This is not a patch to force a pull on a unit you can't properly use.
• If you missed Cyrene: Phase 2 is your chance. Otherwise, bank your jades.
• Outfit collectors: "Karmic Fire of the Distant Shore" requires pulling Mortenax Blade. Factor that into your Phase 1 decision.

Run your Stellar Jade budget through the gacha budget calculator before the banner goes live so you know exactly how many pulls you can guarantee. Check your pity count, confirm your target, and don't spread your resources thin across multiple banners. This patch rewards focused spending — pick your priority and commit. See you on the other side of maintenance.