|Don't be so embarrassed. You're not the only one.|
|— Thomas decides to join the Scout Regiment|
Thomas Wagner (トーマス・ワグナー Tōmasu Wagunā?) was a graduate of the 104th Cadet Corps who fought during the battle for Trost District and was assigned to the middle guard after the Colossal Titan's second attack.
Thomas was initially quite pessimistic about defeating the Titans, believing that humanity ultimately stands no chance, but he would later change his way of thinking after hearing an inspiring speech from Eren. As a cadet, Thomas admitted to still being a bit cowardly, as he was too frightened to immediately act upon witnessing the Colossal Titan for the first time. Despite this, Thomas was also somewhat of a leader, rallying his team into turning their first battle into a hunting competition despite the inherent uncertainty.
On the first night of his time in the 104th Cadet Corps, Thomas and his fellow cadets swamp Eren Jaeger with questions about the fall of Wall Maria after learning that he is a survivor from Shiganshina District.
When Eren retakes his omni-directional mobility gear aptitude test, Thomas is put in charge of operating the training equipment for the test. Eren fails again, and Instructor Sadies orders Thomas to lower him down and exchange harnesses with him, revealing that there is a defect in Eren's.
In the year 848, Thomas is placed in charge of a group of cadets on a wilderness hunt to sustain themselves in times of peace. When it is discovered that the group's ODM gear has been stolen by a band of thieves, Thomas suggests returning to the training grounds to alert Sadies, before agreeing to Reiner's plan to speed up their mission in order to alert Marco Bodt's group of the thieves.
The next day, Thomas and his group come upon Marco's group, who have been engaging the kidnappers, and help them disarm the remaining men.
In the year 849, while the Cadet Corps is performing a mock defense mission in Trost, Thomas takes the opportunity to visit his family.
After graduating, Thomas questions Eren on where he will be applying, arguing that it is pointless to try to fight the Titans as a Scout. Eren then asks him if he is going to give up just because he thinks humanity cannot win, stating that the information gained in battle against the Titans will lead to further hope and that humanity has not been truly defeated yet. Eren's passionate words on behalf of the Scout Regiment inspire Thomas to consider joining the corps as well.
The following day, Thomas' squad is assigned to clean out the cannons atop Wall Rose. As they are working, Thomas reveals to Eren that his words the previous night inspired many of his fellow trainees to consider joining the Scout Regiment. Their conversation is interrupted by Sasha Braus, who reveals that she has stolen meat from the officers' lounge. Despite some reservations, Thomas agrees to partake, celebrating the idea of retaking Wall Maria soon.
Their festivities are cut short when the Colossus Titan appears outside Trost District, knocking them off the Wall with a blast of steam. Eren orders them to attack the Colossus Titan, but Thomas and his comrades are too shocked to immediately react. When they finally climb back to the top of the Wall, they find that the Titan has vanished under a cloud of vapor. Thomas commends Eren for trying to attack the Titan as the Garrison's advance team arrives, and the cadets are ordered to return to HQ.
After the breach, he is assigned to the middle guard along with Eren, Armin Arlelt, Milieus Zeremski, Nack Tierce, and Mina Carolina. He suggests they have a contest on who can kill the most Titans. Noticing an alarming amount of Titans in the middle guard, the squad begins to advance, but are caught off guard by an abnormal Titan which catches Thomas in its mouth and swallows him whole.
Armin would later report his demise to the remaining members of the 104th Cadet Corps, saying he died valiantly in the line of duty.
During the Scouts feast before the mission to retake Wall Maria, Eren remembers Thomas at the time Sasha stole meat.