Slag is an element introduced in Borderlands 2, and is a by-product of the Eridium refinement process. Slag elemental weapons have a chance to coat enemies in slag with slagged targets taking increased damage from all non-slag sources.
In the events of Borderlands: The Pre-Sequel, slag, being newly discovered, is mentioned by Jack only on a single occasion and is not accessible for Vault Hunters, but its effect still can be applied to them by some enemies.
Slag damage has no bonuses or penalties against any non-slag elemental target. In Normal Mode and True Vault Hunter Mode, once a target is slagged, any non-slag damage that target takes is doubled, including effects from elemental affinities, critical hits, melee, and damage over time.
The slag-coating effect lasts 8 seconds on normal enemies. However, the effect only lasts for 1 second on certain raid bosses. Slag elemental enemies and anything that does not take elemental DOT cannot be slagged.
In Ultimate Vault Hunter Mode, Slag effects are boosted to last longer (15s) and cause triple damage (+200%) from non-slag sources. Further slag damage against slagged targets is increased by 50%.
After Handsome Jack began researching the properties of Eridium, he also discovered the mutagenic properties of slag and commissioned an extensive range of tests in the Wildlife Exploitation Preserve. Information given in the mission Doctor's Orders indicates that while many of the tests were conducted on Pandora's wildlife, Jack also ordered the use of human test subjects as well. They were herded into the testing facilities where the scientists were forced to experiment on them under duress. The results were often fatal, but at least in the case of Bloodwing, there are indications that some test subjects survived the process, but were left in a horribly mutated state.
In The Pre-Sequel, Jack uses slag to power the Eye of Helios by feeding it to the Destroyer's disembodied eye. When Moxxi has Jack's Vault Hunters overload it with slag to engage the failsafe, she actually used it to destroy the Eye after restarting it, keeping Jack from using the eye for malicious purposes.
Sources of slag
Though introduced in the mission Rock, Paper, Genocide: Slag Weapons! as a level 7 mission, generic slag weapons will not spawn below level 15. The only exception is the mission item given for use in the aforementioned mission.
- List of Unique/Legendary/Seraph weapons and items that always deal Slag damage:
- List of Slag elemental skills:
- Purple barrels slag nearby targets when destroyed. They also damage nearby enemies like other barrels, but for half of the normal amount.
- Slag weapons have a higher chance (1.5x) to apply elemental effects compared to similar weapons of a different element.
- Almost all enemies can be slagged, although some of them, particularly larger bosses, will not change in appearance.
- Slag elemental enemies cannot be slagged. They resist slag damage.
- Enemies immune to elemental DOT likewise cannot be slagged. These include crystalisks, constructors, The Leviathan, Jackenstein, Piston's Blimp, Badassasaurus, and Saturn.
- Most raid bosses can be slagged, but the effect only lasts for one second. Bosses include Terramorphous, Hyperius, Haderax and Voracidous. The rest can be slagged normally.
- Slag coating stays on top of any other status effect, allowing for easy identification of slagged targets.
- Spiderants, threshers, and sand worms remove their slag effect, along with other damage over time, when they burrow. This applies for Haderax as well.
- When Krieg's Release the Beast is active, his extra melee bonus added to a slagged enemy can do damage upwards of 1 million and can kill non-badass enemies in one hit if a critical hit is achieved.
- In real life, slag is a by-product that is produced when separating metals from ores - it is usually composed of metal oxides and silicon dioxide.
Borderlands: The Pre-Sequel!
As Handsome Jack mentions in the dialogue of Eye to Eye, slag is the substance that allowed him to amplify the power output of the Eye of Helios' enormous laser (actually the eye of Destroyer). Unknown to him, excessive slag usage on the eye could cause space-time instability, and this feature was used by Mad Moxxi to manipulate Jack's Vault Hunters in an attempt to kill all of them and destroy the eye. In gameplay, the damage-increasing role of Slag is replaced with Cryo.
Another presence of slag in The Pre-Sequel is more subtle. Its effects (both visuals and damage multiplication) can be applied to Vault Hunters, though rarely, by ranged attacks of various Guardians, Lost Legion Eternal Magi, and The Sentinel.