Boris Marcus is an infantryman of the Thirteenth Regiment of the Kingdom of Lyferia's Faltra stationed troops at Fort Bridge Ulug.
He is a young man with light-brown hair that is short and ruffled.
He embodies everything one would expect of an ideal knight. His courage and dedication are what motivates Diablo to come to the defense of Fort Ulug during the 100 Fallen assault. He was willing to face an advancing army of 100 Fallen, despite knowing he didn't stand a chance so that the farmers and other civilians could evacuate into the city. Fortunately, Diablo provided interference and drove off the Fallen.
One day after seeing off Rem and Shera to Starfall Tower, sometime later that day he spotted a person coming from Starfall Tower who didn't earlier came through the bridge. He halted that person who "irately" identified himself as Diablo which caused Boris to be frightened. Boris nervously tells Diablo the reason why he stopped him and asked for his social status and objective.
Two days later, he stops the other soldiers from attacking Diablo when they mistook him for a Fallen. Knowing full well that a direct fight with the 100-Fallen army was suicidal, he still refused to abandon his post, fully prepared to die. Fortunately, Diablo stepped up and took on the attack instead. He witnesses Diablo and Shera instantly disappear when Diablo used a teleportation spell.
He and his friend Massa were placed as forward-reconnaissance to watch out for the Great Demon Lord army. He recalls that long ago, Diablo once disappeared from the bridge after talking about teleporting to Faltra.
His childhood friend and fellow guard.