Rainbow Vomit is a Jakobs legendary shotgun in Borderlands 4. The most targeted repeatable route is to defeat Leader Willem at The Excrucible in Carcadia Burn, then use Moxxi’s Big Encore machine in his arena to respawn him. You must first unlock the fight through the Electi quest chain. The shotgun can also appear as a world drop, but the available guides do not establish that route as an efficient farm.
Where to get Rainbow Vomit
Leader Willem is the weapon’s dedicated source. Find his arena at The Excrucible in Carcadia Burn, near Grindstone of the Worthy. PC Gamer locates it east of Grindstone, beside the path into Terminus Range. PC Gamer’s Rainbow Vomit guide and Mobalytics’ weapon guide describe the boss route.
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The fight is not immediately available: complete the Electi quest chain to reach Willem. The cited guides list the quests in this order:
- Enter the Electi Part 1
- Enter the Electi Part 2
- The Council Divided
- A Traitor Within
- The Mole’s Gambit
The first Willem encounter occurs during The Mole’s Gambit. Follow the active quest markers through the missions; Shacknews’ Leader Willem walkthrough provides additional objective-by-objective directions.
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How to farm Leader Willem repeatedly
- Finish The Mole’s Gambit and defeat Willem during the quest.
- Return to Willem’s arena at The Excrucible.
- Use Moxxi’s Big Encore machine there to respawn the boss.
- Defeat Willem again and check the loot. Repeat the Encore reset and fight if you want more chances at the shotgun.
The guides establish this repeat method, but do not provide a verified per-kill drop chance, cash cost, or kill time. A Willem kill is a chance to obtain Rainbow Vomit, not a guaranteed drop; the available evidence does not support a reliable estimate of how many attempts it may take.
Other possible sources
Rainbow Vomit is also reported as a world drop, meaning it may come from other loot sources rather than Willem specifically. Lootlemon lists it in the game-wide shotgun pool, while PC Gamer also identifies Weekly Wildcard missions as a possible source when the activity’s rewards include legendary shotguns. Neither guide quantifies those alternatives or shows that they are more efficient than farming Willem. Check the current in-game Weekly Wildcard reward preview, since activity rewards can change.
Lootlemon’s item listing identifies Rainbow Vomit as a base-game legendary shotgun; the base game is required to collect and equip it.
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What to check on each Rainbow Vomit drop
The shotgun’s special effect is called Color Spray. It fires multiple elemental droplets, but the rolled elemental types can vary between drops. Lootlemon describes Corrosive, Cryo, and Incendiary droplets, while PC Gamer and Mobalytics note that the elemental combination can change. Inspect the weapon card on your own drop rather than assuming every copy has the same elements.
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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11If you get more than one, compare the rolled elements, damage, and part configuration against your build. The guides do not establish a single best roll or a universal build ranking. PC Gamer notes that Jakobs shotguns ricochet critical hits, though Rainbow Vomit can also roll other manufacturer parts.
Drop odds and what to expect
The cited guides and item database do not establish an authoritative current drop percentage for Leader Willem. No dependable expected kill count or time-to-drop can be calculated from them. Treat the Encore loop as a repeatable way to make more attempts at the dedicated source, not as a guaranteed or timed farm.
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