Borderlands includes four character classes, each with unique skills, abilities and back stories. As a character gains experience and levels up, their basic statistics, such as health totals and accuracy, will increase. Each class also has three unique focus skill trees to develop. There is also an accessory item type specific to each class. The four classes are:
- Mordecai - The Hunter, who has skills that enhance Sniper Rifles and Pistols. He sends his pet Bloodwing to attack enemies from above. The 'Bloodwing' is an AI-controlled aerial unit that will operate semi-independently of the hunter. Sniper tree: improves sniper abilities; Rogue tree: improves special ability; Gunslinger tree: improves pistol and melee abilities.
- Roland - The Soldier, who is well suited to using Combat Rifles and Shotguns. He can deploy an automatic Scorpio Turret to attack enemies, which operates independently, allowing the soldier to hide behind cover or attack enemies while his turret attacks enemies. Infantry tree: increases effectiveness with weapons particularly combat rifles and shotguns; Support tree: increase Roland's defensive abilities with shields, and improve his Scorpio Turret's cooldown, increase its burst fire count and allow his turret to support the Soldier and his teammates by constantly resupplying their ordnance; Medic tree: abilities that allow the Soldier to rapidly replenish his health and his allies' even in the midst of heavy combat.
- Lilith - The Siren, who has advantages using SMGs and Elemental weapons. Touched by ancient alien power, her ability is 'Phasewalk': She can shift into a different dimension and become invisible for a few seconds, and when she enters or exits that state she releases a shockwave of energy which damages nearby enemies. Controller tree: improves survivability and disables foes; Elemental tree: improves her ability to use weapons and inflict Elemental damage; Assassin tree: increases lethality with weaponry and melee combat.
- Brick - The Berserker, who loves to do nothing more than pound enemies with his fists. Other than that, is a master of blasting his foes with explosive heavy weapons. His ability is 'Berserk', in which he uses his fists to pound his enemies to death, and gains large increases to his survivability and speed to achieve that end. Brawler tree: increases melee damage capabilities; Tank tree: massively increases toughness and survivability; Blaster: improves explosive damage and abilities with weaponry, especially Rocket Launchers.
Borderlands 2 redraws the playing field with a new set of character classes that players may select from. The original cast from Borderlands return in supporting roles.
The Borderlands 2 classes are:
- Maya - The Siren, who can Phaselock her enemies in a stasis bubble to help control the field of battle; Cataclysm tree: Skills offering a wide range of damage types; Harmony tree: Defensive upgrades focusing on character health values. Defensive upgrades based around damage prevention. Motion tree: Upgrades to Phaselock for crowd control. Mixture of defensive and offensive abilities.
- Salvador - The Gunzerker, who can unleash a wild barrage of gunfire as he launches into a gun-waving battle frenzy; Brawn tree: Focuses on physical toughness; Gun Lust tree: Increases weapon stats and grants various abilities. Wrath tree: Stat bonuses and abilities tied to simultaneously wielding a gun in each hand.
- Axton - The Commando, who can deploy a Sabre Turret, dramatically increasing the available firepower on the field of battle. Guerilla tree: General combat enhancements well suited to being in the thick of the fight; Gunpowder tree: Damage enhancements suitable for long range fighting; Survival tree: Defensive enhancements.
- Zer0 - The Assassin, who can deploy a holographic decoy and cloak himself entirely from view. Bloodshed tree: Skills to upgrade Zer0's close combat effectiveness; Cunning tree: A wide array of utilities and damage effects; Sniping tree: Weapon enhancements with a particular emphasis on sniper rifles.
Borderlands 2 has been created with the capacity to accommodate additional characters from DLCs:
- Gaige - The Mechromancer, who can summon a powerful battle robot to do the wetwork for her. Best Friends Forever tree: Skills designed to enhance survivability; Little Big Trouble tree: Elemental damage focused, especially shock; Ordered Chaos tree: Skills that focuses on close range damage and restoring health and shields as you kill enemies.
- Krieg - The Psycho, who can go into a bloody rage. He puts his guns away then pulls out his 2-handed Buzz Axe and gains 500% melee damage. Bloodlust: Skills are focused around kill skills and abilities which increase with Bloodlust stacks, such as increased damage, reload speed, and grenades. Mania: Focuses on melee attacks, including allowing Krieg to morph into a Mutant Badass Psycho. Hellborn: Focuses on fire damage and giving perks such as damage resistance to Krieg while he himself is on fire.
- Regardless of mentions about weapon preferences, all characters may use any type of weapon throughout the game. For example, Roland might have a need to use a sniper rifle for long-range targeting, or the Hunter could certainly use shotguns against close range targets. Also, regardless of aforementioned "ideals" for each character, all of them have skills which allow for great variations in gameplay. For instance, Mordecai, with certain talents taken and various benefits from COMs and weapons, can deal isolated melee strikes equal to or even greater than Brick in some cases. However the preferences refer to abilities that improve effectiveness with particular weapon types, like Roland's Scattershot, Mordecai's Caliber or Brick's Wide Load.
- The main characters are often referred to as "Vault Hunters" in the story, due to the their role in the course of events as soldiers of fortune seeking the Vault and its rumoured treasures.
- Judging from their dialogue and interactions with each other Roland appears to be the leader of the original Vault Hunters.
- In the mission Wanted: Dead!, displayed text from each character highlights their individual personality traits. Lilith's cursive script is signed off with a kiss mark and dots her "I"s with hearts, Mordecai uses a hasty scribble, Roland prints plainly and neatly in capitals, and Brick's writing is a barely legible and childlike scrawl.
- The classes all have three skill trees, which allows them to become more powerful characters as they advance in level.
- Although not an official member of the team, the NPC Michael Mamaril makes mention of himself also being a Vault Hunter before giving the player a weapon.
- Fiona and the Unnamed Man that appear on the Tales from the Borderlands trailer are pointed out by Marcus of not being Vault Hunters despite their intentions of performing something that normally a Vault Hunter would do.