Borderlands 4 Best Eridium Farm Guide (And where to spend it)

Eridium is the purple currency which you can see if you hover over your currencies box in your inventory.

Best Method of Farming Eridium

Bounties. Specifically, Vile Bounties.

Vile Bounties do not become available until you beat the story and unlock UVH first, so don't worry about farming Eridium before this point. Once you do unlock UVH you will need to be playing on at least UVH 1 to gain access to Vile Bounties.

What are Vile Bounties?

At every Safehouse or major town, there will be a contracts board, of which you can except up to 5 total contracts at any one time from across Kairos. These contracts come in various types: Bounty, Vile Bounty, Patrol, Collect, Acquire and Trace. However we're only interested in Vile Bounties today. These are the most easily identified as they will display in a bright purple, unlike the blue all the other bounties use.

Farming

To begin, choose your starting Safehouse (I like the bottom left Fade Fields one, Abandoned Post) and check for any Vile Bounties. Then fast to each of the regions Safe Houses and Launchtown picking up every purple bounty available and do them. Plan an optimal route to pick them up using silos and safehouses as fast travel points. Once you've done them go to the next region and go again. DO NOT search Dominion. Dominion appears to have a very low chance at Vile Bounties.

After you have toured the full map, or until Contract boards start giving reduced Contracts, Save Quit and start over.

This method will land you 30-45 bounties an hour. At 400 Eridium per bounty you will be bringing in over 10'000 Eridium an hour, up to 20'000 with a good run of luck.

Altneratively

You can choose a specific safehouse to base on, South Carcadia Burn 'Makeshift Chalet' is the best here, as most Vile Spawns here are either a short drive, or close to another Silo or Safehouse fast travel point. This method reduces time spent driving, but has you save quitting a lot more, so less ideal for co-op or slower load times.

Either way will net you so much Eridium you won't know what to do with it after an hour or two, so let's talk about that.

Where to Spend Eridium

There are 3 primary ways of spending Eridium

1. Swapping Firmwares from character to character. At 60-75 eridium a pop this is very cheap, and it's unlikely you'll have any issues affording this. Though is still an important step to min-maxing your builds. The Firmware machines are unlocked as soon as you beat the main story campaign.

2. Respeccing your specialisations. At a whopping 5000 Eridium a respec this looks to be eye wateringly expensive, thankfully with our farm here it only takes 20-30 minutes to afford.

3. Big Encore. This is where the majory of your eridium will be going. Every week there is a Big Encore boss somewhere on the map, unlocked after beating the main story. Big Encore will around double the bosses' health and massively increase the drops rates of their loot. Going from around 5% per individual item, to about 25%.

Big Encore costs 100 eridium a run, so a casual hours worth of Eridium farming will net you 100-200 Big Encore Runs. Because of the increased drop rates this activity is also the best method in the game to farm for Shiny 'Posphene' weapons.