Mylius Zeramuski was of average height with bluish gray eyes and ash blond hair. He wore the typical uniform of a members of the 104th Training Corps.
Mylius seemed shy and cautious; he warned Eren when he was running off to avenge Thomas Wagner for fear of his safety and inexperience. However he showed bravery when charging in with his squad to save his comrade.
Mylius Zeramuski graduates training as a member of the 104th Training Corps. After the second attack of the Colossus Titan, he is assigned to a middle guard squad in Trost District with Eren Yeager, Armin Arlert, Mina Carolina, Thomas Wagner, and Nac Tias.
Shortly after the squad's deployment, the group is attacked by an abnormal Titan, which results in the death of Thomas Wagner. This causes Eren to attack the aberrant in a rage. Mylius warns Eren not to go alone, but he does not listen and a Bigmouth Titan bites his leg off which in turn causes his squad to pursue it to try and help him. This leads to Mina Carolina being knocked against a wall by the Titan and eaten by a Peering Titan. Armin can then only watch as fellow trainees Nac Tias and Mylius are caught and eaten by the Titan while the peering Titan crushes Mina's head in it's jaws. Armin later reports Mylius' demise to the remaining members of the 104th Training Corps, saying he died valiantly in the line of duty.