Jacob

Jacob is the spiritual leader and healer of the Remnant—the protectors of the Divine Source. He has a daughter named Sofia, who is the Military Commander of the Remnants. Her mother and Jacob never got married, as revealed in one of Jacob's memoirs found in the valley.

History
During the story, Lara and Jacob form a close and strong friendship after encountering each other while imprisoned, followed by a few times they saved each others lives. Lara found herself trusting Jacob enough to reveal to him her feelings about the Divine Source and her father's suicide.

It is later revealed that Jacob is just another alias used by the Deathless Prophet, who has been alive all these generations and centuries, living with the remnants in the valleys in the mountains that surround the city of Kitezh.

Death
Ultimately, when Trinity besieged the ruins of Kitezh one final time, Jacob arrived at the Chamber of Souls, killing the last Trinity soldier who came to inform Ana that their troops were dying, only to be shot several times by Ana. As the Deathless Ones surround them while Lara held the Source in her hand, she destroyed the artefact to stop them and also to keep the source from other hands such as Trinity, causing the immortals to disintegrate into ash and dust. With his immortality finally gone, Jacob thanked Lara for giving him his ending, before peacefully disintegrating.

Powers & Abilities

 * Supernatural Powers: He was exposed to the "Divine Source" and therefore gained ageless immortality, unlimited stamina & extreme regenerative powers, that resurrect him from death. Through practice over using his powers, he also learned how to heal any mortal being within several seconds, just by using the limitless regenerative energies inside his body. These "Divine" powers, seems to have also made him stronger, faster & durable than an average human being.
 * Warfare Expert: Like most of his people, he too is a highly skilled guerrilla fighter, marksman, stealth tactics, craftsman & hand-to-hand combatant.

Trivia

 * After finishing the game, some villagers around the valley can be overheard talking about Jacob and the source, one saying "Jacob and the source are gone, what are we protecting now" meaning they all knew about Jacob, he hadn't tried to keep himself and his immortality a secret to his people.
 * When it is revealed that he is the Prophet, Jacob tells Lara that he can still "feel pain, that he is still human, just without the human end."
 * At the end of the game, when the player returns to the ruins of Kitezh, the Deathless Ones are still encountered instead of Trinity soldiers. Either this means that some power of the Divine Source is still active, or the game developers overlooked this so the player could fight the Deathless Ones at anytime. There is a slim chance that Jacob is still alive even if the former is true, as he had completely turned to dust.
 * Jacob's voice actor is Philip Anthony-Rodriguez, who also voiced for Fallout 4, which had come out at the same time as Rise of the Tomb Raider.