I've died to this boss grind more times than I can count honestly and tbh that's kind of why I'm writing this up Borderlands 4 bosses are where you get your legendary weapons class mods artifacts basically all the good stuff and knowing the mechanics the loot tables and the fastest kill strats turns a stupidly long 10 minute slog into a 30 second farm ngl and I mean that literally you can shave off that much time once you know what you're doing so here's every major boss with what they drop and how to melt them on Mayhem 10 and 11 or whatever Mayhem level you're running
Base Game Story Bosses
The Seer (Final Boss)
I've fought The Seer probably more than any other boss in the game and tbh it still catches me off guard sometimes Location: Vaulthalla Health Type: Shield + Armor (phase 1), Armor + Flesh (phase 2) so you kind of need to switch elements mid fight which sucks honestly Notable Loot: Plasma Coil SMG, Tizzy pistol, Seer Class Mod all pretty much worth the grind imo So the strat for phase 1 is basically this The Seer teleports around the arena like a maniac and fires these homing projectiles that'll wreck you if you stand still I've found that staying mobile and hugging cover is literally the only way to survive the arena has 3 pillars that block most attacks but you know sometimes the hitboxes get weird and stuff like that Then phase 2 gets real ugly the Seer charges up this massive laser that sweeps the whole arena and I mean it covers damn near everything so you gotta hide behind these glowing crystals that pop up and even then your mileage may vary honestly Strategy: Shock damage for the shield phase corrosive for the armor phase fire for the flesh phase Kill time on Mayhem 10 is about 2 to 4 minutes with an optimized build maybe longer if you're like me and forget to swap elements halfway through who knows
Katagawa Jr. (Mid-Game Boss)
Katagawa Jr is honestly one of those bosses that's either a 30 second joke or a 10 minute nightmare depending on whether you know the trick Location: Atlas HQ, Promethea Notable Loot: Sand Hawk sniper rifle, Katagawa Class Mod both kind of worth farming imo So here's the thing Katagawa splits into clones and you gotta destroy the clones to find the real one and tbh the first time I tried this I was shooting randomly for like 5 minutes before figuring it out Shock weapons literally one shot the clones which is awesome and the real Katagawa gives off this faint electromagnetic pulse when hit so look for that visual cue it's pretty obvious once you see it Strategy: Kill time is like 30 seconds with a shock Monarch or Light Show basically nothing to it once you get the pattern down
The Agonizer 9000
The Agonizer 9000 is in the Guts of Carnivora on Pandora and ngl this was one of my favorite fights first time through Notable Loot: Backburner rocket launcher, Agonizer Class Mod, White Elephant artifact all pretty solid honestly Strategy: So when the glowing core is exposed that's when you unload everything you've got Also destroy the spinning blades first because those things will mess you up if you ignore them I learned that the hard way The Agonizer has a massive crit spot too so basically any weapon with high fire rate just melts it corrosive for the armor phase obviously Kill time is about 45 seconds once you know the pattern maybe faster if you're running a cracked build
DLC Bosses
Hemovorous the Invincible (Raid Boss)
Hemovorous the Invincible is tbh the most annoying fight in the game and I kind of love it for that Location: Darkthirst Dominion, Pandora (Director's Cut DLC) Entry Cost: 500 Eridium per attempt which honestly sucks when you're still learning the fight and burning through your eridium stash Notable Loot: Atlas Replay, Company Man artifacts with those hyper specific manufacturer bonuses that are basically build defining So this is a two phase fight with the highest health pool in BL4 and I mean it's absolutely massive Phase 1 Hemo spawns Varkid eggs that hatch into badass Varkids and you need to kill the eggs immediately like don't even think about ignoring them because it gets out of control fast and then you're dead and you get the idea Then Phase 2 at 50 percent health Hemo enrages and gains damage resistance while spawning even more eggs and all that so you need to keep your distance and just sustain fire Strategy: Iron Bear Moze or Barrier Zane is what I'd recommend for survivability otherwise you're gonna have a bad time Kill time on Mayhem 10 solo is about 10 to 15 minutes maybe longer if you're not fully optimized who knows honestly it's a slog but the loot makes it kind of worth it
General Boss Farming Tips
Honestly element matching is pretty much the most important thing you gotta know Blue health bar means shock damage Yellow means corrosive Red means fire or you get the idea Matching the right element deals 2.5x damage on Mayhem 10 and 11 and ignoring this is basically why most people struggle with boss fights tbh I've wasted so many runs before I figured this out
Also you should always check your Mayhem modifiers before starting a farm run avoid anything that reduces your primary element damage or increases enemy health reroll at the Mayhem console until you get favorable modifiers it takes like 30 seconds and saves you so much headache ngl I used to skip this step and wondered why my damage was garbage
And here's the thing about kill speed I've learned after farming these bosses for hundreds of hours a boss you can kill in 30 seconds is worth farming even with a 10 percent drop rate but a 5 minute kill needs like a 30 percent plus drop rate to be time efficient so basically farm the bosses you can melt fast and don't waste time on the ones that take forever or whatever your time is literally more valuable than a slightly better drop chance imo