Vault 13 Overseer

Jacoren is the Overseer of Vault 13 in 2161.

Background
When the Vault's only functioning water chip got damaged and shut down, he sent one of the vault dwellers, who later became known as the Vault Dweller, into the wasteland to find a replacement chip. In the course of his adventure, the Vault Dweller ended up defeating the mutant threat, and was subsequently expelled from Vault 13, as Jacoren thought that he would ruin the Vault Experiment by convincing people to leave the Vault.

Despite the Vault Dweller's exile, many people chose to follow him into the Wasteland. It's not clear what happens to Jacoren after the exile of the Vault Dweller. He can try to stop those who want to leave and eventually be tried and sentenced to death for his crime, probably after the dwellers learned about his involvement in the Experiment, or he can be killed at the hand of the Vault Dweller after his/her goodbye speech.

He was fully aware of the Vault Experiment program conducted by the Enclave, and therefore tried to do everything to keep the Vault closed for 200 years, just as the program dictated. As it is quite unlikely that he could have been more than 100 years old, the knowledge about the experiment was probably passed to him from the previous Overseer, most likely one of his parents.

Other interactions
Overseer Jacoren tasks the player with the 3 main quests in the game: finding the water chip, killing the Master and destroying the vats in the Mariposa Military Base. There is little time for chatting with him, since he just questions as to why you are not looking for the chip.

If the "player" gets into combat with Jacoren then they will die no matter what as he has infinite health due to Jacoren being a major character.

Effects of player's actions
If your character has the Bloody Mess Trait, the title Berserker, or a low karma, right after the Overseer's goodbye speech at the end of the game, the Vault Dweller will automatically put away his weapon, draw a pistol and shoot the Overseer in the back. It is also possible to kill the Overseer by pressing A key to initiate combat just after his speech, and putting him down with one critical shot.

Final speech
"You've done it! It's... wonderful. Amazing! I'm so proud of what you've accomplished, what you've endured." "There's no way the people of the Vault can ever thank you enough for what you've done. You've saved all our lives. Who knows, maybe even saved the human race. [The Overseer sighs.] That makes the rest of this even harder." "Everyone will want to talk to you. Every youngster will look up to you, and want to emulate you. And then what?" "They'll want to leave. What happens to the Vault if we lose the best of a generation? What if we are the only safe place in the world? You just gave us back all these lives... I can't take the chance of losing them." "I've made a lot of tough decisions since I took this position. But none of them harder than this one. You saved us, but you'll kill us. I'm sorry. You're a hero... and you have to leave."

Appearances
Jacoren appears only in Fallout. He is a talking head voiced by Ken Mars.

He was also to appear in the canceled Fallout movie, where he was to be revealed as the founder of Vault-Tec and the man who started the Great War.

Behind the scenes
Anyway, when big dumb Larry drew the straw, maybe the Overseer saw a way to rid their limited gene pool of some really bad alleles.'' - Tim Cain at DAC forum
 * ''I always thought of Fallout's story of drawing straws was something the Overseer thought of. "Look, someone has to go outside, and they may die out there, so let's draw straws". Someone, probably not the Overseer since he wouldn't have gone outside no matter what, demanded that EVERYONE draw a straw in order to be truly fair. But to be honest, the vault dwellers were simply terrified of going outside, and terrified people do not always make the wisest decisions.