Samuel Hayden

Samuel Hayden is the Chairman of the UAC who oversaw the Argent energy research projects at the UAC Mars Base. A supporting character in Doom (2016) and Doom Eternal, he helps guide the Doom Slayer.

History
Samuel Hayden was born to the powerful Hayden family and was a very prodigious intellectual and philanthropist. He is accomplished in several scientific fields, including thermodynamics, electromagnetic theory, and nuclear sciences. He was the founder of the Samuel Hayden Foundation, which promoted the sponsoring of young scientific talent and funding scientific programs in schools and colleges. After Hayden was appointed as General Director of the Global Science Council, the UAC recruited him. Soon after Argent Energy was discovered on Mars, Hayden subsequently took over the leadership of the UAC and began the construction of the Argent Tower on Mars.

During construction of the Argent Tower, Hayden was diagnosed with a stage 4 incurable brain cancer and left with a few months to live. Hayden avoided his death by transferring parts of his brain into a 3-meter tall mechanoid body, allowing him to be virtually immortal. It was implied that Hayden chose this form for his expeditions into Hell. After his "rebirth", Hayden was appointed as Project Director of the Argent Facility and under his leadership humanity embraced an Argent-based technological revolution as Argent Energy is integrated into all forms of technology. By the time the Argent Tower finished construction in 2127, Hayden personally dispatched the first Argent package to Earth.

Hayden was also the benefactor of Olivia Pierce whom he helped in appointing her to the Global Science Council and later the Head Director of the UAC's Lazarus Project after showing the Helix Stone to her. However, Hayden soon came to regret for recruiting Pierce as his former protegee became religiously obsessed with Hell and her mind gradually grew deranged. Hayden led the first manned expedition into Hell in 2145 in which he discovered the Doom Slayer, simply called "Doom Marine", in the Kadingir Sanctum. He had the Marine recovered and kept him personally under his watch, planning to use him as part of a contingency plan against Hell. After recovering the Marine, Hayden came to blows with Pierce and grew more suspicious of his disgruntled colleague, who secretly formed a pact with Hell's Dark Lord to bring an invasion into the human realm.

Doom (2016)
After Pierce betrayed Hayden and planned to open the gates of Hell, Hayden awakened the Doom Marine and tried to persuade him to assist him in stopping Pierce. However, he is harshly rebuffed twice at the beginning of the game, though Hayden claims to be willing to accept full responsibility for Hell's invasion. Hayden was able to gain the Marine's partial cooperation after cutting off his access to the satellite communications array and offering information that he seeks, although in their attempt to stop Pierce, the Marine later destroyed the Argent energy stations rather than temporarily disabling them as Hayden asked, much to Hayden's irritation.

Hayden eventually meets the Doom Marine face-to-face in his office following the latter's return from Hell and the destruction of the Argent Tower. He explained to the Marine about the ongoing demonic invasion of the facility through the still-open Hell portal, and the need to pursue a new way into Hell in order to locate the Crucible, an artifact that can control the source of Argent energy known as "The Well," and stop Pierce's plans. He instructed the Marine to go to the Lazarus Labs to find the Helix Stone and a powerful weapon.

But Hayden also intended to restart Argent energy production as soon as possible, but also knew the Marine would disapprove, as he demonstrated by his testy behavior at the Argent Facility. After the Doom Marine killed Pierce and stopped Hell's invasion, Hayden summoned the Marine to the facility via a dimensional tether. He then traps the Doom Marine, taking the Crucible from him to continue exploiting Hell's resources for the sake of humanity's progress. Hayden admitted that he cannot kill the Doom Marine, but he will not allow him to stand in his plans, before teleporting the Doom Marine to an unspecified location. Before he does so, however, Hayden states his certainty that he and the Doom Marine would meet again.

Doom Eternal
In 2150, Hayden suddenly resurfaced on Earth before the Allied Nations Council during the time the demonic invasion of Earth had already begun. Hayden recounted the events on Mars to the AN Council before offering to help lead humanity against Hell by providing them his technologies and the Crucible, the last remaining source of Argent Energy in existence.

The Council appointed Hayden as the Lead Director of the Armored Response Coalition. Under his leadership, Hayden re-purposed the UAC facilities on Earth to produce and supply Argent technology and advanced armaments to the ARC. As the war against Hell grew more dire, Hayden was subsequently given full command over all resistance efforts. With humanity deprived of its Argent-dependent energy grid after the loss of the Well, Hayden invented a method of Argent-Synthesis, a synthetic replication that could recreate the high-yield capability of Argent Energy. Using the Crucible's hidden power, Hayden utilized the artifact as an Argent conductor to restoring the production of Argent energy to Earth.

Hayden later fell in battle during Operation Hellbreaker, a powerful counterattack that he planned and ultimately ended in failure. His robotic torso, which suffered the loss of its right forearm and legs, was retrieved by ARC soldiers. Hayden was tended and monitored by a skeleton crew of scientists, who safeguard his body along with the Crucible, in the ARC Complex. The scientists were unable to revive Hayden as they have no knowledge to access his main cortex due to its "alien" make up.

The Doom Slayer, on the advice of VEGA, sought for Hayden's aid in finding the location of the final Hell Priest, Deag Grav. Upon the Slayer arriving at the facility, Hayden had long anticipated for the Slayer's return and specifically told his caretakers to give the Crucible to the Slayer. When the Slayer reunited with Hayden, he roughly took the torso and threw him into a portal to the Fortress of Doom. There, Hayden's consciousness is transferred into the Fortress's mainframe, as his body is similar and compatible to the architecture, and awoke. From there, Hayden then explained to the Slayer of Deag Grav's whereabouts in Sentinel Prime and that getting there is through the only functional slip-gate, located in the core of Mars, in the lost city of Hebeth. Though Hayden voiced his concerns on the difficultly of gaining access to the core of Mars, he is exasperated over the Slayer's direct approach to use the BFG-10000 to shoot a hole into Mars' surface. Following afterwards, Hayden guided the Slayer throughout his journey.

After the Slayer killed Grav, the Khan Maykr attempted to stop him by shutting down the Fortress of Doom. However, the Slayer utilized the Crucible's latent Argent energy to reactivate the fortress. Hayden was left amused by the irony of the fact that the Crucible's power source, which the Slayer sought to eradicate from Earth, became his aid to save it. Hayden then helped guide the Slayer in retrieving his own Crucible to slay the Icon of Sin and stopping the Maykrs from consuming Earth.

Trivia

 * Despite having been diagnosed with "incurable brain cancer", Samuel Hayden had his frontal and temporal lobes transferred to his new body. It is possible that these parts of his brain were free of cancer, and that he chose to replace his whole body rather than simply replace the cancerous parts of his brain with cybernetic equivalents.
 * A head-and-shoulders image of Samuel Hayden's original human body can be seen at the bottom of the lobby stairs in Advanced Research Complex among various other UAC scientists.
 * Hayden is stated to be functionally immortal in his robotic body thanks to brain rejuvenation techniques. Currently, he is over 130 years old.
 * When Hayden walks away to his office, the player is given control of their weapons and can shoot Hayden. However, the bullets strike an invisible force field of sorts, dealing no damage to Hayden, who simply shrugs it off while telling the Slayer to save his ammunition.
 * His name may be taken from a character cut from Doom 3 but depicted in the Doom 3 novels: General Hayden. Their personalities and history are not similar, however.
 * Samuel Hayden along with the Doom Slayer are said to be the only humans to have survived a trip to Hell and back.
 * Doom Eternal alludes to a possible otherworldly origin for Samuel. The Seraphim Samur Maykr shares the same voice actor as Hayden, and the ARC scientists state that Samuel's body is "alien" and that they can't figure it out. Similarly, when brought back to the Fortress of Doom, VEGA states that Hayden's body has similar a architecture to the ship, suggesting he is of Maykr design. In addition, in Urdak, VEGA glitches out for a second when connected to the mainframe of the Maykr capital, asking "Am I the Father?", suggesting that 'the essence of the Father' that was stolen from the Maykrs may very well have been used to create VEGA.
 * This can also be seen as both characters share a near-exact quote. While Hayden in Doom (2016) states "It's a gift. Take it, it will give you strength, help you on your journey..." after giving the Slayer an Argent Cell, the Seraphim, before granting the Slayer his powers using the Divinity Machine, states "I offer you a gift. Take it. It will give you strength... help you along your journey."
 * It is also stated in History of the Sentinels - Part IX that only a "true Sentinel Warrior King" can activate a Crucible, yet Samuel is able to do so at the end of the 2016 Doom, further suggesting he is not of Earthly origin.