Harlowe is built around Entanglement: any enemy tagged by her action skill shares gun and skill damage with other entangled targets. Her three trees each anchor a different playstyle. If you want fast boss kills, lean on the Creative Bursts tree with CHROMA Accelerator. For room clears, the Seize the Day tree turns Zero‑Point into a crowd-control engine. And if you prefer a team aura with high uptime and ricochets, Cosmic Brilliance’s Flux Generator can carry co‑op while staying dangerous solo.

Best overall: Radiation CHROMA Accelerator (bossing/endgame)

This is the most reliable endgame path for Harlowe. The goal is simple: fire CHROMA Accelerator to stack damage, then pour that stored power into your gun through the Neutron Capture augment for a short burst window.

Slot Choice Why it matters
Action Skill CHROMA Accelerator Fires a traveling energy pocket (cryo on pass, manual/auto radiation detonation) to prime your burst.
Key Augment Neutron Capture Transfers a portion of Accelerator’s dealt damage to your gun as bonus radiation for a short duration.
Core passives (red) Field‑Ready Prototype, Elementary, Enriched, Poisoned Sun, Chain Reactor, Fissile Launcher, Dirty Bomb, Mechanical Brilliance Stacks action‑skill and radiation damage, adds darts/explosions, and ramps skill damage during fights.
Capstone (red) Demon Core Accelerator fires homing radiation darts as it travels and automatically irradiates entangled enemies.
Support passives (blue) Make Extraordinary, Bright Future, Ripple Effect; optional Parallel Circuit, Quantum Immortality Critical chance for skills (affecting Neutron Capture), big fire‑rate after triggering, chain Entanglement on kill; gun damage and sustain are optional adds.
Weapons Fast‑firing Vladof ARs/SMGs; Katagawa’s Revenge; Convergence; Luty Madlad High rate‑of‑fire squeezes more Neutron Capture damage into the window; listed legendaries excel at burst and ad‑clear.
Shield Watts 4 Dinner, Super Soldier, Protean Cell, Firewerks All viable: mobility/regen (Watts/Super Soldier), boss DPS (Protean Cell), mobbing missiles (Firewerks).
Repkit Shiny War Paint or Triple Bypass War Paint juices fire rate/movement; Triple Bypass can edge out for raw DPS if you find strong rolls.
Class Mod Skeptic (general), Scientist (group), Atomic Driver (pure bossing) Skeptic is the all‑rounder; Scientist leans into team utility; Atomic Driver adds unnecessary but potent boss damage.
Ordnance (optional) Throwing Knife with Penetrator augment Piles on single‑target damage; not required for the build to work.
Enhancements Bounce Pass (Jakobs ricochet), Daedalus (shotgun fire‑rate) Match the enhancement to your main weapon for higher hit counts per second during the window.
Firmware 3× High Caliber + 2× GOOJFC Pierce/sustained DPS from High Caliber; cooldown and action‑skill damage from GOOJFC.
Specializations I Am A Gun, A Honed Mind, Now With Caffeine, Riddle You This Helps the Accelerator scale with gun buffs, adds action‑skill crits, reduces cooldown via Repkits, and ramps gun damage in combat.

Gameplay loop:

  • Open with CHROMA Accelerator and aim to hit as many targets as possible to front‑load stored damage.
  • During Neutron Capture’s window, hold the trigger on a very fast AR/SMG; fire‑rate outruns flat gun damage here.
  • While waiting on cooldown, pop your Repkit to trigger Now With Caffeine, or keep shooting statused targets to maintain uptime via your class mod and passives.
Tip: If you swap targets, tag them with Accelerator first so Neutron Capture applies to the new focus. The more enemies you pass through and detonate on, the bigger your gun burst gets.

Mobbing: Zero‑Point cryo stasis (crowd control and chain kills)

Zero‑Point locks down rooms by suspending enemies, then spreading Entanglement and damage between them. You can run it two ways: a classic ricochet‑and‑spread setup, or a slam‑centric variant that pulls enemies into a cryo blast.

Slot Choice Why it matters
Action Skill Zero‑Point Places a target in stasis; reactivate to slam for a small explosion and reposition control.
Augments Strange Attractor (core), Inertia (variant) Strange Attractor ricochets bullets and entangles on crits to snowball; Inertia chains stasis on death for non‑stop uptime.
Core passives (blue) Periodic Table Flip, Ripple Effect, Precision Engineering, Too Coolant for Schoolant, Cryodynamics, Concurrence, Control Group, Freeze Frame Spreads Entanglement, boosts crits and cryo, extends stasis per entangled enemy, and refunds duration/cooldown on kill.
Power spike (blue) Triple Point Huge cryo damage bonus on entangled enemies; the build’s primary damage lever.
Capstone Falling Bodies (ricochet route) or Cold Plunge (slam route) Falling Bodies adds another stasis target and slams all when stasis ends; Cold Plunge creates a singularity + cryo explosion on slam.
Support (red) Cyclotron, Fuzzy Math (light picks) Extra fire‑rate and status application from the top of Creative Bursts to keep momentum.
Weapons Jakobs (natural ricochet), Rainbow Vomit, Kaoson, cryo shotguns/SMGs Ricochets multiply shared damage across frozen packs; cryo primaries stack Triple Point.
Shield Firewerks or sustain‑oriented options Firewerks helps automate cleanup; swap to defensive picks for tougher arenas.

Gameplay loop:

  • Mark a central threat with Zero‑Point, then crit nearby enemies to entangle and ricochet damage through Strange Attractor.
  • Hold aggro while Control Group and Concurrence extend your stasis chain; slam when packs bunch or to finish waves.
  • Use cryo weapons to fully exploit Triple Point, then move the bubble to the next cluster.
Note: The slam‑first “cryo slam” variant leans on Inertia and Cold Plunge to constantly pull and explode enemies. It’s blistering for mobs and weaker against single targets.

Co‑op and aura play: Flux Generator “Nuclear Winter” (inside/outside damage)

Flux Generator drops a mobile field that entangles, grants overshield, and flips your damage type depending on whether you’re standing inside it or not. It’s the most team‑friendly Harlowe kit and still hits hard solo.

Slot Choice Why it matters
Action Skill Flux Generator Projects an energy field that deals cryo over time, entangles enemies, and gives allies overshields.
Key Augment Nuclear Winter (swap in after early leveling with Blue Giant) Inside the field you deal bonus cryo; outside you deal bonus radiation for a duration. Applying either element entangles.
Core passives (green) Decoherence, Refraction, Excited State, Creative Overflow, Latent Charge, Mains Hum, Distribution Function, Harlowe’s Certainty Principle, Critical Funding More damage to entangled enemies, ricochets, guaranteed crit follow‑ups after action‑skill damage, overshield‑based gun damage, bigger shields, shield return, handling, and magazine refills on crit.
Capstone Violent Horizon (solo) or Group Study (team) Violent Horizon adds projectiles and a singularity on retrigger; Group Study replaces the field with HALO sidekicks that buff allies (stackable).
Weapons Elemental SMGs/shotguns; Katagawa’s Revenge for ad‑clear Cryo inside the field, radiation outside—swap or use multi‑element options to keep status effects rolling.
Firmware High Caliber + GOOJFC (mix 3/2) Maintains hit volume and keeps action‑skill damage/cooldown flowing between tosses.

Why this can feel “infinite”: with Nuclear Winter active, enemies damaged by the field trigger Excited State, making your next shot an automatic critical. Critical Funding then refills magazines on crits. In practice, that loop sustains fire on high‑ammo weapons, especially launchers and fast SMGs, while overshields from Distribution Function and Mains Hum keep you upright.

Gameplay loop:

  • Toss Flux Generator onto the densest pack and fight inside the field for cryo and auto‑crit follow‑ups.
  • Step out to ride the temporary radiation buff, then retrigger to reposition—use Violent Horizon’s singularity to gather stragglers.
  • In groups, Group Study follows teammates to keep their fire rate and reloads spooled while you orbit and clean up.

Pointing your build the right way

Harlowe scales absurdly well off fire‑rate during CHROMA windows, cryo bonuses on entangled targets, and overshield‑based gun damage around Flux Generator. Here’s a compact selector to keep your priorities straight:

Goal Tree & skill Damage levers to prioritize Comfort picks
Boss melts Creative Bursts · CHROMA Accelerator Neutron Capture, Demon Core; fire‑rate (Cyclotron, Bright Future); radiation stack (Enriched, Poisoned Sun, Chain Reactor, Fissile Launcher, Dirty Bomb) Parallel Circuit (gun damage), Quantum Immortality (regen)
Mobbing Seize the Day · Zero‑Point Ripple Effect, Concurrence, Control Group; Triple Point; cryo damage (Cryodynamics, Unstable Ice‑otope) Strange Attractor or Inertia to taste; Cold Plunge for slam routes
Co‑op aura Cosmic Brilliance · Flux Generator Nuclear Winter; overshield damage (Creative Overflow, Latent Charge); Excited State + Critical Funding; Decoherence Refraction (ricochets), Mains Hum (capacity), Distribution Function (shield returns)

As you push higher UVH ranks or tougher activities, don’t be afraid to trade a bit of top‑end damage for sustain: Quantum Immortality, Keep Ice On That, and overshield loops around Flux Generator add a lot of comfort with minimal DPS loss.

If you only pick one path, run the radiation CHROMA Accelerator build. It’s the cleanest bossing setup in Harlowe’s kit, and it doesn’t need a specific legendary to work—just a high fire‑rate weapon and disciplined use of the action‑skill window. Zero‑Point and Flux Generator round out the toolbox for arenas and co‑op, and you can swap between them at respec for the activity at hand.