Children of the Vault is the first quest you'll have to face during your adventure with Borderlands 3. In this section of the Guide, you will find a walkthrough of this story mission.
The entire adventure begins with a meeting with Claptrap. Your first task is simply to follow him. The robot will first show you to the character creation panel. Then, you will need to unlock the further passage. You do this with the lever located in the vehicle to the right of the barricade.
Keep following Claptrap, you will get to the chest with weapons. Take its contents. Then, your friend will go under the door of the crypt and begin to negotiate the entrance. You can search the neighborhood in the meantime, in order to get additional equipment.
At that time Claptrap will be captured by a large magnet. You will have to follow him, simultaneously eliminating enemies. Use the surrounding elements of environment as cover.
After the battle, Claptrap will ask you to find and equip some shields. You will find them on the roof of one of the containers located in the central part of the square.
Then, go towards the steel door. Shiv is waiting for you behind them. The fight against him should not be the most challenging. If you keep your distance, he will only attack with a shock wave. The direction of these is clrealy telegraphed by the cracks on the ground.
After defeating Shiv, go up the stairs. They will lead you to the control panel for the magnet. There, you will be able to turn off the power and release Claptrap.
Finally, go back to your friend and repair him.