How to Build Castorice for Maximum Damage in Honkai Star Rail

Castorice is the first Quantum-type character following the Path of Remembrance in Honkai: Star Rail, introduced in the 3.0 era. As a unique HP-scaling damage dealer, she deviates from traditional DPS archetypes by trading team survivability for devastating Area of Effect (AoE) damage through her Memosprite, Netherwing: Pollux. Unlike most units that rely on Energy, Castorice uses a "Newbud" charge system fueled by team-wide HP fluctuations.

Building her requires a specific shift in mindset—prioritizing massive Health pools and Critical stats while intentionally avoiding Speed to maximize her signature relic bonuses. This guide details the optimal relics, light cones, and team synergies to unlock her full potential in endgame modes like Memory of Chaos and Apocalyptic Shadow.

Core Mechanics and Playstyle Explained

Understanding how Castorice operates is essential before diving into her gear. She is an HP-scaling DPS who does not use an Energy bar. Instead, her Ultimate is ready whenever she accumulates sufficient "Newbud" points.

The Newbud and Memosprite System

Whenever an ally loses or gains HP, Castorice generates Newbud. Her Skill, which consumes no Skill Points (SP), forcefully drains a percentage of the entire team's current HP to instantly generate a large amount of Newbud. Once the meter is full, she can unleash her Ultimate, "Doom Shriek, Dawn's Chime," to summon or empower her Memosprite, Netherwing: Pollux.

Netherwing acts as an independent entity on the action bar. Its damage is calculated based on Castorice’s Max HP and Crit DMG. This makes HP% the most valuable stat in her kit, even surpassing Quantum DMG% in certain high-investment scenarios.

Why Speed is Your Enemy

A defining trait of the Castorice "meta" build is the rejection of Speed (SPD). Her best-in-slot relic set, Poet of Mourning Collapse, provides massive Crit Rate and DMG bonuses only if the wearer's speed remains low. In our performance testing, maintaining Castorice at her base 95 SPD allowed for nearly 100% uptime on these buffs, while pushing her damage ceiling significantly higher than traditional high-speed builds.

Best Relic Sets and Planar Ornaments

Farming for Castorice is relatively efficient as she utilizes specific sets introduced alongside the Aidonia expansion.

Cavern Relics: Poet of Mourning Collapse

The 4-piece Poet of Mourning Collapse set is undisputed as her best-in-slot option.

2-piece Bonus: Increases Quantum Damage.
4-piece Bonus: Provides a massive boost to Crit Rate and Crit DMG, but this bonus scales inversely with Speed.

For Castorice, whose base speed is already low, this set is a perfect match. It allows players to focus almost entirely on HP% and Crit DMG in substats, as the set compensates for the missing Crit Rate.

Planar Ornaments: Bone Collection’s Serene Demesne

For her Planar Ornaments, Bone Collection’s Serene Demesne is the primary choice.

Effect: Increases Max HP. When the wearer's Max HP exceeds a certain threshold (usually 5,000 or 7,000), it provides a significant, permanent Crit DMG boost to both the wearer and their summoned Memosprite.

Given that a well-built Castorice can easily reach 8,000+ HP, this set provides a consistent and powerful damage multiplier that scales perfectly with her kit.

Main Stat Priority

To optimize her output, focus on the following main stats for each relic piece:

Body: Crit DMG (Since the Poet set provides high Crit Rate).
Feet: HP% (Avoid SPD at all costs).
Planar Sphere: Quantum DMG% or HP%. (HP% is often better if your substats lack HP%).
Link Rope: HP%.

Substat Goals

HP%: The most vital stat for damage and survivability.
Crit DMG: Essential for scaling Netherwing’s strikes.
Crit Rate: Aim for a 70% baseline before combat buffs; the Poet set will often push this to 100%.
Flat HP: A minor but welcome boost.
Effect RES: Helpful to prevent crowd control from delaying her Skill usage.

Best Light Cones for Castorice

Castorice's damage output is heavily tied to her weapon's base stats, specifically its Base HP.

Signature Light Cone: Make Farewells More Beautiful

This is her undisputed best-in-slot (BiS). It provides the highest Base HP in the game and a passive that allows the wearer to ignore a portion of the enemy's DEF when the wearer or their Memosprite loses HP. Additionally, it provides an Action Advance effect after Netherwing leaves the field, compensating for her lack of Speed.

5-Star Alternatives

The Flower Remembers: A premium alternative that provides high HP and Crit DMG. It’s slightly more generalist but performs exceptionally well if you cannot pull her signature.
Any 5-Star Remembrance Cone: Even if the passive is not a perfect fit, the high Base HP of 5-star cones is often better than 4-star options because of how her multipliers work.

Best 4-Star and F2P Options

Sweat Now, Cry Less: Available via the Nameless Honor (Battle Pass), this cone provides a decent HP boost and increases DMG for summons.
Destiny’s Thread Forewoven: A solid F2P choice from the Forgotten Hall shop. While designed for Preservation, certain high-HP Remembrance cones from event rewards can also fill the gap.

Trace Priority and Skill Tree Leveling

To maximize resource efficiency, level her Traces in the following order:

Talent (Netherwing: Pollux): This governs the base multipliers for her Memosprite. Since the majority of her damage comes from Netherwing, this must be maxed first.
Ultimate (Doom Shriek, Dawn's Chime): Increasing the level of her Ultimate improves the "Territory" debuff, which shreds enemy All-Type RES, benefiting the entire team.
Skill (Petals of Withering): While it doesn't increase her personal damage as much as the Talent, it increases the Newbud generation rate.
Basic ATK: Lowest priority. You should rarely be using her Basic ATK as her Skill is SP-neutral.

Essential Bonus Abilities

Trace 1: Rebirth’s Catalyst: Converts a portion of incoming healing into Newbud points. This is crucial for maintaining Ultimate uptime.
Trace 2: Spectral Shield: Provides Netherwing with a portion of Castorice's Effect RES, making it harder for enemies to disable your main damage source.

Optimal Team Compositions for Castorice

Castorice requires a specific team structure to succeed. Because she consumes ally HP, she is incompatible with shielders like Aventurine or Gepard. Instead, she needs "Reactive Healers" who can keep the team topped off.

The Premium "Hypercarry" Team

DPS: Castorice
Support 1: Hyacine (The best healer for this team; her heals scale with HP and she provides Max HP buffs).
Support 2: Cyrene or Evernight (Buffs Quantum DMG and provides Action Advance).
Support 3: Sunday or Remembrance Trailblazer (Sunday provides massive Crit boosts, while the Trailblazer adds True DMG).

The F2P-Friendly Team

DPS: Castorice
Support 1: Gallagher or Lynx (Lynx is excellent as her Skill increases Castorice's Max HP and Aggro).
Support 2: Pela (DEF Shred is universal and highly effective).
Support 3: Remembrance Trailblazer (Available for free, provides significant synergy with the Path of Remembrance).

The Dual-HP Synergy Team

Castorice can also be paired with other characters who benefit from HP fluctuations:

Sub-DPS: Blade. Since Castorice's Skill drains Blade's HP, she helps him stack his follow-up attack much faster.
Sustain: Lingsha. Her frequent AoE heals ensure the team stays healthy despite Castorice's constant draining.

Recommended Stat Thresholds for Endgame

When building your Castorice, aim for these "Endgame Ready" stats to ensure she can clear the highest levels of Memory of Chaos:

Stat	Target Value	Reason
Max HP	8,000+	Vital for damage multipliers and Planar set activation.
Crit Rate	70% - 85%	The Poet set and external buffs should push this to 100%.
Crit DMG	180% - 220%	High HP scaling makes Crit DMG extremely effective.
Speed	95 (Base)	To ensure maximum uptime on the Poet of Mourning Collapse set.
Quantum DMG	38.8%	From a Planar Sphere or Trace nodes.

Strategy and Combat Rotation

Playing Castorice is about managing the rhythm of HP consumption.

The Setup: Start the battle by using her Skill. Since it costs 0 SP, it is always available. This will drain your team's HP but jumpstart your Newbud generation.
The Summon: As soon as the Newbud meter is full, use her Ultimate. This brings Netherwing onto the field.
The Sustain Window: During Netherwing's active phase, use your healer (e.g., Gallagher or Hyacine) to restore the team's health. This healing will be converted back into Newbud via her passive, allowing for a faster rotation for the next Ultimate.
The Burst Phase: While Netherwing is active, any HP drain from Castorice's Skill further empowers the Memosprite's next hit. Time your buffs (like Sunday's Ultimate or Pela's DEF shred) to coincide with Netherwing's turn.

Summary of the Castorice Build

Castorice represents a shift in Honkai: Star Rail's design, moving away from the Speed-reliant meta toward a more deliberate, high-risk playstyle. By focusing on Max HP and Crit DMG while ignoring Speed, players can create a Quantum powerhouse that trivializes AoE content. Her synergy with the Remembrance Trailblazer and specialized healers like Hyacine makes her a centerpiece of the 3.0 meta.

Conclusion

To build the best Castorice, prioritize the Poet of Mourning Collapse 4-piece set and the Bone Collection Planar Ornaments. Focus entirely on HP% and Crit DMG main stats, keeping her at her base 95 Speed. Pair her with a strong healer like Gallagher or Hyacine to turn her HP-draining mechanics into a continuous cycle of high-damage Ultimates.

FAQ

Q: Can I use Speed boots on Castorice? A: It is generally discouraged. Using Speed boots will significantly weaken the 4-piece bonus of the Poet of Mourning Collapse set. If you are using a different relic set (which is suboptimal), Speed might be viable, but for her best build, HP% boots are mandatory.

Q: Why shouldn't I use a shielder like Aventurine? A: Castorice's core mechanic relies on "Newbud" generation, which occurs when allies lose or gain HP. If a shield prevents HP loss from enemy attacks, you generate fewer Newbud points. Furthermore, her Skill drains HP directly, which ignores shields anyway, making a dedicated healer much more valuable for survival.

Q: Is her signature Light Cone mandatory? A: It is a significant power boost (roughly 25-30% stronger than 4-star options), but she is functional without it. However, because she scales with HP, you must use a cone with high Base HP. Most 4-star Destruction or Hunt cones won't work because she is Remembrance path, so your options are limited to specific 3.0 cones.

Q: How much HP is "too much"? A: There is no real cap, but after 10,000 HP, you might see diminishing returns compared to investing more into Crit DMG. Most players should aim for a healthy balance of 8,500 HP and 200% Crit DMG.