Mechanics

Three separate systems make your numbers go up in Borderlands 2, and they run on different clocks. Skill points belong to one character and reset when you respec. Badass Rank belongs to your whole account and never goes away. Eridium is a currency you spend on the backpack and ammo capacity that every build quietly depends on. This guide covers all three, plus the challenges that feed them and the exploits people use to skip the grind.

Skill trees

All six playable characters have one action skill and three trees, and our skill trees guide lists every skill in each of them with its per-level numbers.

The skills that read as small percentages compound faster than they look. Axton's Guerrilla tree adds shots, duration and accuracy to the turret until Scorched Earth gives it 22 rocket pods per volley and Gemini gives him two turrets at once, while Survival ends at Grit, a flat chance to survive a killing blow. Maya's Motion tree turns Phaselock into crowd control with Converge, which drags everything to the locked target. Which of those you want depends on the build, and our builds guide makes the picks per character.

Challenges and Badass Rank

Challenges are the game's second progression bar. Completing them raises Badass Rank, Badass Rank hands out tokens, and tokens buy permanent stat boosts that apply to every character on the account, including ones you have not made yet. There are 274 Badass Tokens available in total once the DLC challenges are counted, according to our Badass Tokens guide.

Most of them come from ordinary play. Our challenges guide works region by region, and the pattern repeats: every area has a Cult of the Vault challenge for finding its hidden Vault symbols, a kill-something-without-taking-damage challenge, and a collectible sweep. Make Boom Go Boom wants Boom and Bewm dead without a hit from Big Bertha, Fireproof wants Flint dead without taking dragon breath, and Man's Best Friend wants Boll down without hurting his snow skags. Bosses respawn, so a challenge you fail at a low level is simply one to come back to.

The tougher ones are attached to boss fights, and our boss challenges guide goes through those individually, since a skill challenge in the middle of a boss fight usually means beating it in a way that is harder than beating it.

Farming tokens quickly

Eridium

Eridium is capped at 500 and spent at the Black Market on ammo capacity and backpack slots. Our Eridium farming guide recommends buying backpack space first, because carrying more loot is what makes every other farm worthwhile.

Twenty Eridium purchases also close out the Whaddaya Buyin? challenge, worth a further 166 Badass Rank, so the two systems feed each other. As for where the Eridium comes from, there are four routes our page rates.

Achievements worth building for

Most achievements happen on their own. Unseen Predator does not: it wants melee kills from stealth, which means a Zer0 built around Deception and the melee skills that surround it. Our Unseen Predator guide lays out that build specifically, and it is worth 20 points.

The duplication exploit

Item duplication survived from the first Borderlands, and our duplication guide covers both versions. One needs a friend and the duel interface; the other uses the cross-save feature on PC and PlayStation. The same trick applies to money, which is how people fund the slot machines that pay Eridium. It is an exploit rather than a feature, so treat it accordingly.

Frequently asked questions

How many Badass Tokens can I get?

274 in total with the DLC challenges included, and the stat boosts they buy apply to every character on the account.

What should I spend Eridium on first?

Backpack slots, then ammo capacity. The cap is 500, upgrades run 4, 8, 12, 16 and 20 Eridium per level, and 20 purchases also completes a challenge worth 166 Badass Rank.

Can I respec my skill points?

Yes, which is why our build pages are worth trying rather than agonising over. Skill points are the reversible half of a character; the gear behind them is the part that takes farming.