Nac Tias had dark brown hair, which was styled back in a somewhat spiky pattern. He had medium brown eyes and was somewhat tall when compared to the average of the other trainees from his squad. He wore the typical uniform of a member of the 104th Training Corps with a gray shirt underneath.
Nac appeared to be a warm-hearted person who cared a lot about his friends, which he did not seem to have much trouble making.
StoryColossus Titan, he is assigned to the middle guard including Eren Yeager and Armin Arlert in the Trost District. 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 Titan in a rage, but his carelessness causes him to get his leg bitten off by a Bigmouth Titan. This causes his squad to pursue and try to help him but results in their death at the hands of the same Titan, except for Mina Carolina who was hit by the Titan and then eaten by a Peering Titan. Armin would later report his demise to the remaining members of the 104th Training Corps, saying he died valiantly in the line of duty.
His death would later be avenged by Eren in his Titan form when he kills the Titan responsible for Nac's demise by punching and repeatedly stomping it into the ground after it attempts to attack him.