Marcus

Origin

Originally, Marcus was a member of the Master's super mutant army. This army, which began in 2103, was created by exposing humans to large amounts of F.E.V.: the Forced Evolutionary Virus. While the results were unpredictable, the mutants shared many common traits: they were taller and bulkier than normal humans, their strength and endurance were extremely high,

they were sterile, and the F.E.V. ceased their aging, essentially making them immortal. What differentiated certain mutants is that most of them were reduced to mindless thugs and monsters, while certain subjects retained their intelligence and ability to think for themselves.

In 2162, the Vault Dweller killed the Master and destroyed the base which contained the vats of F.E.V. Once their leader was gone, the majority of the mutant army headed for the East Coast. Certain mutants, particularly the aforementioned who retained their intelligence, wanted to join the humans in rebuilding the continental United States. Marcus was one of these mutants.

Jacob and Broken Hills

In the summer of 2185, after wandering aimlessly for years due to the defeat of the Master, Marcus came across Jacob. Jacob was a Brotherhood of Steel paladin who had sworn himself to the destruction of the super mutant army; needless to say, the two didn't see eye to eye. For a few days they shot at each other, and when they ran out of ammo, they resorted to beating the crap out of each other.

Eventually, when they realized they couldn't one up the other, they gave up, not seeing the point in killing each other anyway. The two begrudgingly started travelling together. On their travels they argued over the Master and his ability to truly take over the world, the veracity of certain Brotherhood of Steel data, and whether Jacob would have been improved if he were dipped in a vat of F.E.V.. The two acquired quite a following as they wandered through the wasteland; in Marcus' words, the refugees figured 'if they weren't safe travelling with a Steel Knight and a Super Mutant, they weren't safe anywhere.'

In the Fall of 2185, Jacob, Marcus and the refugees (which included humans, ghouls and other intelligent super mutants) founded the community of Broken Hills. By the time Fallout 2 begins, Jacob has long since died of old age, and Marcus, who by then considered him his best friend, misses him dearly.  

Fallout 2

In Fallout 2, the Chosen One comes across Marcus, now serving as the sheriff of Broken Hills. If the player solves most of the quests in Broken Hills, he can ask Marcus to join him on his quest to find the G.E.C.K.. Marcus is proficient in big guns and energy weapons, he can carry a great deal but he cannot equip armor, his body being too big for armour built for humans. When the Chosen One completes his quest, Marcus leaves him and ventures off to the East Coast in search of more survivors from the Master's army.
 

Fallout: New Vegas

In 2088 Marcus is residing in the Mojave Wasteland, at Jacobstown (named in honor of his old friend,) of which Marcus partially built. The town was built to help the Nightkin overcome their mental problems. Actor Michael Dorn provides the voice for Marcus in Fallout: New Vegas.