Near the end of Tales from the Borderlands episode 5, The Vault of the Traveler, the player must pick three teammates to join the fight against the vault guardian. Only select characters will be available to pick from depending on the choices you’ve made throughout the rest of the game. Here’s what you need to do throughout each episode in order to unlock each character as a playable option.
Right at the end of episode 1 you must warn Felix about the bomb in the suitcase. If you do not, he will die. If you do, he’ll be around for the finale and give you some additional funds before the end.
Near the beginning of episode 3 Vallory will ask Fiona who is responsible for the Vault Key deal going south. So long as you don’t blame August, he will show his appreciation at the end and be willing to help you out.
During episode 3 Athena attempts to kill Cassius. If you stop her from doing so he will be your ally at the end, willing to assist in the battle against the vault guardian.
Late in episode 3 Fiona goes to help Athena fight Brick and Mordecai. When Mordecai asks what you’re doing, you must tell him you’re a vault hunter. Upon doing so Zer0 will hear of this, and be intrigued enough to fight alongside you.
Near the beginning of episode 4 when talking to Springs in Scooter’s garage, make sure to tell her that Athena loves her. In doing so you save their relationship, for which Athena will be grateful and willing to help out at the end.
In episode 4, following Scooter’s sacrifice, you must honor Scooter’s wish by launching his satellite. As a close friend and colleague, Janey Springs will appreciate your gesture and be unlocked for the final fight.
Aside from the friends you’ve made along the way, you can also choose to hire a vault hunter if you’ve got enough money. The only problem is, even if you save every dollar you pick up over the course of the game you still won’t have enough to afford one. *In order to hire a vault hunter you must warn Felix about the bomb in episode 1 and save him. Then when you are choosing your team in episode 5, pick Felix. He will give you a massive amount of cash, which you can then use to hire the single available vault hunter to aid you in the final battle.