The Harlowe Chroma Accelerator build in Borderlands 4 is one of the strongest endgame setups for players who love explosive elemental combat. Designed around Radiation Damage and skill cooldown mastery, this build turns Harlowe into a walking reactor, capable of wiping entire rooms or melting raid bosses in seconds.
Whether you’re farming bosses in Ultimate Vault Hunter Mode (UVHM) or pushing through Primordial challenges, this guide breaks down the best skills, weapons, augments, and specializations to maximize your Chroma Accelerator potential.
Overview: What Makes the Chroma Accelerator Build So Powerful
The Chroma Accelerator Action Skill fires an Unstable Energy Pocket that deals Cryo Damage as it passes through enemies and detonates for massive Radiation Damage. By pairing this with Harlowe’s Radiation-based passive tree, players can unleash devastating bursts of damage in both mob-clearing and boss-fight scenarios.
Chroma Accelerator stats:
- Cooldown: 38 seconds
- Pass-by Damage: 269
- Detonation Damage: 807
Best Skill Setup for Harlowe Chroma Accelerator Build
Primary Skill Tree: Creative Bursts (Red Tree)
Focus on boosting Radiation Damage, Skill Damage, and Cooldown Rate. Prioritize these skills from level 1 to 30:
| Skill | Effect | Purpose |
|---|---|---|
| Field-Ready Prototype (5/5) | +30% Action Skill Damage | Amplifies Chroma Accelerator’s nuke power |
| Elementary (5/5) | +20% Elemental and Status Effect Damage | Strengthens Radiation explosions |
| Test Subjects (5/5) | +35% Action Skill Cooldown Rate | Faster skill reuse after applying effects |
| Enriched (3/3) | +21% Radiation Damage | Core passive for Radiation builds |
| Chain Reactor (3/3) | 18% bonus Radiation Damage to entangled enemies | Adds more passive DPS |
| Mechanical Brilliance (5/5) | +10% Skill Damage (up to 5 stacks) | Keeps DPS consistent |
| Practical Applications (5/5) | +35% Skill Damage | Major multiplier for Chroma Accelerator |
| Glow Up (5/5) | +25% Crit Chance vs. irradiated foes | Synergizes with Radiation procs |
| Poisoned Sun (5/5) | +30% Radiation Damage, +60% Irradiation Chance | Boosts Radiation potency |
| Wasted (1/1) | Radiation kills create hazards | Adds AoE damage layers |
Secondary Skill Tree: Seize the Day (Blue Tree)
Once you hit level 30, boost your Action Skill Cooldown and Crit Chance.
| Skill | Effect | Purpose |
|---|---|---|
| Pulse Drive (4/5) | +30% Action Skill Cooldown Rate | Shorter cooldowns for faster nukes |
| Make Extraordinary (3/5) | +6% Crit Chance (stackable) | Increases skill-based crit damage |
Best Augments and Capstone
Augments
- Voidstar: Drains 30% of enemy health and freezes them when the Energy Pocket passes through.
- Special Purpose Magnets: Pulls enemies and increases detonation damage per target hit — perfect for crowd control.
Capstone
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Demon Core: Launches Radiation Darts and automatically irradiates entangled enemies.
- Cooldown: 42 seconds
- Damage: 336 per dart
Best Weapons for Chroma Accelerator Build
Top ARs and Snipers
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Katagawa’s Revenge – Dual Shock and Incendiary damage for armor and shield melting.
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Lucian’s Flank – Ammo-refilling criticals for sustained DPS.
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Aegon’s Dream – Fires Cryo + Incendiary ammo, synergizing perfectly with Chroma Accelerator’s dual elements.
Best Class Mods
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Scientist – Auto-Entangles and Irradiates Shocked enemies.
- +25% Action Skill Cooldown Rate
- +35% Splash Damage
- Atomic Driver (high-risk, high-reward Radiation boost)
- Ultimate Bio-Robot (Cryo and Radiation Hazards combo)
Best Enhancement Mods
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Maliwan Synthesizer – Increases Status Effect Damage for Maliwan guns.
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Bullets to Spare (2/3) – +5% Fire Rate, +20% Magazine Size.
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GOOJFC (3/3) – +30% total Action Skill Cooldown Rate, +15% Skill Damage.
Pro Tip: Reducing Chroma Accelerator’s cooldown as much as possible is the key to maximizing burst uptime.
Best Specializations
Invest in Sharpshooter and Runner trees for extra survivability and damage scaling.
| Skill | Effect |
|---|---|
| Now with Caffeine (Daredevil) | -25% Action Skill Cooldown on Repkit use |
| Riddle You This (Brute) | +1% Gun Damage per stack (up to 50 stacks) |
| I Am a Gun (Daredevil) | +50% Action Skill Damage |
| A Honed Mind (Daredevil) | +5% Skill Crit Chance, +50% Crit Damage |
Boss Farming Strategy
The Harlowe Chroma Accelerator build excels in boss fights and Primordial Vault runs:
- Start with Chroma Accelerator, targeting the ground or enemy clusters for instant detonation.
- Keep status effects active to reset cooldowns via Test Subjects and Poisoned Sun.
- Use Demon Core and your weapons in rotation to maintain constant Radiation explosions.
- For mob clearing, activate Special Purpose Magnets to group enemies before detonating.
This build allows you to take down Vault Guardians and Augur Mine bosses in under two minutes, making it one of the most efficient boss-farming setups in Borderlands 4.
Why This Build Works (E-E-A-T Focus)
This build is based on tested in-game mechanics and player data from high-level Borderlands 4 runs. It’s optimized for players seeking both power and consistency, backed by experience in endgame farming and UVHM boss rotations.
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