Arc Knives might be the weakest of Rafa's Action Skills in Borderlands 4, but that doesn't mean it is completely useless. It works perfectly well for fighting big groups and grounded bosses, but making an Arc Knives build that doesn't immediately get you killed can be pretty tricky.
This is an endgame Arc Knives build for Rafa in Borderlands 4 that can melt health bars with Corrosive, Kinetic, and Incendiary damage while face-taking hits like a champ. It's basically useless against flying enemies, but it can chew up anything that's on the ground no problem.
Borderlands 4: Best Vex Build (Incarnate)
The best Siren build for Vex in Borderlands 4 depends on what players are looking for, but this OP Incarnate build is definitely a must-have.
Best Arc Knives Rafa Build - Skills
|
Skill |
Description |
|---|---|
|
Green Tree |
|
|
Handshake Deal |
Increases Gun and Melee Damage. Good all-around boost. |
|
Dial In |
Melee gains a stacking Melee Critical Hit Chance buff when he hits enemies with melee attacks. Stacks are lost when he hits a crit. |
|
Saldar |
Melee crits gain lifesteal. Important for face-tanking enemies in the late game. |
|
Altered Cabron (Augment) |
Rafa restores health when he kills an enemy with Arc Knives. When Rafa heals, he gains Bonus Corrosive Damage on all attacks and gains movement speed. This effect stacks. |
|
El Borracho |
Rafa deals increased Corrosive Damage while his Action Skill is active. This bonus increases the longer his Action Skill remains active. |
|
Sustainable Energy |
Rafa gains Health Regeneration while Overdrive is active. The regeneration gets stronger based on how much time Overdrive has remaining. |
|
Galvanic Panic |
Melee attacks with Arc Knives launches STRM Gliders that deal Corrosive Damage based on the number of Marked enemies. Killing enemies while Arc Knives is active restores its duration. Activating Blade Fury launches a volley of STRM Gliders. |
|
Red Tree |
|
|
Shield Barriest |
Rafa gains bonus Shield Recharge Rate and improved Shield Recharge Delay while Overdrive is active. |
|
Juerga |
Action Skill Duration is restored when Rafa critically hits an enemy. |
|
Resiliencia |
Rafa gains Damage Reduction while Overdrive is active. |
|
Asymmetric Warfare |
Indirect Projectiles gain bonus damage. This affects all Action Skill Weapons, Thrown Weapons, and projectiles not fired from your gun. |
|
Errant Spark (4/5) |
Indirect Projectiles deal bonus Incendiary Damage. If they already deal Incendiary Damage, double the bonus. |
Get five points into each of the skills listed above except for Errant Spark. You won't have enough skill points to max it out until Gearbox decides to add more.
To summarize, this build is all about keeping Arc Knives (and Rafa) active for as long as possible. The HP regen from Sustainable Energy and the lifesteal from Saldar are enough to keep Rafa alive even under heavy fire, provided that he is attacking something and is equipped with the right shield. Meanwhile, Galvanic Panic and Juerga will keep Arc Knives up for a very long time, but this depends on how often Rafa can crit every four seconds and how quickly he can kill enemies. Much like the Peacebreaker Cannon build for Rafa, this one has very high Overdrive uptime.
Also, this build makes use of a couple of weird but important interactions with Asymmetric Warfare and Errant Spark:
- Arc Knives fits under the Indirect Projectiles description despite not being a projectile-based weapon.
- Errant Spark's bonus Incendiary Damage also applies to Arc Knives.
Arc Knives is practically useless against anything that is flying over Rafa, so you'll still want something that can boost your gun's damage. Vitriol is an excellent skill for this — it gives bonus Corrosive Damage to your next gun shot after reloading. Get a weapon that reloads frequently, then get 4 points into Vitriol for that sweet bonus damage.
For whatever reason, the Hostile Acquisition skill that gives Lifesteal to Indirect Projectiles does not work on Arc Knives. This could be a bug, though.
Specialization Skills
As an Action Skill-based build that uses melee attacks, you'll want to use the following Specialization Skills:
- Riddle You This (Brute): Gain Gun Damage every time you deal Gun Damage.
- Bullet Train (Runner): Increase Gun Damage by 15% while walking. The bonus increases the faster you are moving, and you can now Hipfire while Sprinting.
- Now With Caffeine (Daredevil): Using your Repkit restores 25% of Action Skill Cooldown.
- Down But Not Out (Sharpshooter): You can aim while in FFYL, and you suffer no accuracy penalties.
Riddle You This is here to boost your Gun Damage up some more when you aren't slicing things up with Arc Knives. If you would rather use strong single-shot weapons like the Noisy Cricket pistol or the Hot Slugger shotgun, then use In the Zone from the Sharpshooter branch instead.
As of writing, Arc Knives is terribly inconsistent with how it interacts with stats. Bear Arms, which should increase your Melee Damage based on Gun Damage bonuses, does not affect Arc Knives. However, it does scale with I Am A Gun, which does the same thing but for Action Skills. If you want to beef up your Arc Knives damage even more, take this over Down But Not Out.
Recommended Weapons and Items
As mentioned earlier, pick between an automatic weapon or a hard-hitting one depending on what Specialization Skill you want to use. Again, the single-shot or quick-reload weapons will benefit a lot from the Vitriol skill (if you decide to take that), but otherwise, just use whatever you like. We do recommend getting a gun with a strong underbarrel attachment like Maliwan's Beam Tosser, Ripper's Shrapnel Cannon, or Jakobs' grenade launcher.
Must-Have Legendary Items
- Onion Shield: This is an armor segment-based shield that grants you two seconds of invulnerability when a segment breaks.
- AF1000 Repkit: If you ever lose Arc Knives for whatever reason, an AF1000 with the Accelerator perk will reduce your Arc Knives cooldown significantly.
- Firewerks Shield: Allevieates some of your weakness against flying targets by spawning rockets when your shield segments break, or when you kill enemies.
Class Item
The Dancer Legendary Class Item doubles Rafa's Overdrive bonuses, making it great for this build since Overdrive will always be active when Rafa is using Arc Knives. This isn't mandatory, however, and getting a Class Item with the right stats and skills is going to be more important.
Speaking of stats and skills, look a Class Item with any of the following:
- El Catrin (Skill): Sliding grants Action Skills bonus Shock Damage and increases Rafa's Critical Hit Damage.
- First Impression (Skill): The first shot after reloading deals bonus damage.
- Blowout (Skill): Applying a Mark or scoring crits with Action Skills makes enemies explode and launch Corrosive projectiles.
- Gun Damage
- Action Skill Damage
- Elemental Damage
- Bonus Shields
Firmware Sets
There are plenty of Firmware Sets in Borderlands 4, and while these aren't totally necessary to make this build work, you'll want to use some regardless. The best Firmware sets for Arc Knives are:
- Rubberband Man: Grants Damage Reduction and Lifesteal.
- GOOJFC: Improves Action Skill Damage and Cooldown Rate
- Godkiller: Deal more damage and take less damage from Badasses.
- Deadeye: Increases Gun Accuracy and Gun Critical Hit Damage.
Borderlands 4
- Released
- September 12, 2025
WHERE TO PLAY
- ESRB
- Mature 17+ / Blood and Gore, Intense Violence, Sexual Themes, Strong Language, In-Game Purchases, Users Interact
- Developer(s)
- Gearbox Software
- Publisher(s)
- 2K
- Engine
- Unreal Engine 5
- Multiplayer
- Online Co-Op, Online Multiplayer
- Cross-Platform Play
- Yes - all platforms
- Prequel(s)
- Borderlands 3, Borderlands 2, Borderlands
- Franchise
- Borderlands
- Number of Players
- 1-4 players
- Steam Deck Compatibility
- Unsupported
- PC Release Date
- September 12, 2025
- Xbox Series X|S Release Date
- September 12, 2025
- PS5 Release Date
- September 12, 2025
- Nintendo Switch 2 Release Date
- October 3, 2025
- Platform(s)
- PlayStation 5, Xbox Series X, Xbox Series S, Nintendo Switch 2, PC
- OpenCritic Rating
- Strong
- Local Co-Op Support
- Yes
- X|S Optimized
- Yes
