Deltoff is a man with short side-swept brown hair and a clean-shaven face with bright eyes. As an aristocrat, he wears a black suit over a white shirt, as well as a cravat.
Deltoff is a selfish man, putting his own personal gain over the welfare of the Walls' citizens. He, along with the rest of the council, prepare to disband the Scout Regiment and execute its commander for his own personal interest. Deltoff creates a pretense that disbanding the Scout Regiment would be in the interest of the people; however, this claim is shattered by the ruse that Wall Rose has been breached. He agrees to shut out the citizens of Wall Rose, showing that he acts in his own interest and not by those of the people.
Deltoff is a part of an audience held with other nobles in the presence of King Fritz. They are concerned with Rod Reiss's suggestion that the royal government begin giving out food rations to the Walls' citizens, but Rod insists that the expenditure was necessary to boost the citizens' morale, and to improve the royal family's public approval.
Deltoff attends another meeting with the assembly to discuss what information they have been able to gather. He inquires as to whether they have been able to determine what information Nick leaked to the Scouts, to which the assembly denies. The meeting is then interrupted by the arrival of a message from Rod, informing them that he has captured Eren Jaeger and Historia Reiss and is making his move against the Scouts.
Following Erwin's arrest, the assemblymen hold a meeting to discuss what information could be gained from his interrogation. Their meeting is interrupted with news that Erwin has arrived for his trial, and the men all set out for the court room, ready to sentence him to death.
The assemblymen all dodge Erwin's arguments for why the Scout Regiment should be allowed to continue operating, instead focusing on his supposed breach of the Charter of Humanity in refusing to turn Eren over to the government. Although Erwin argues that Eren is vital to reclaiming Wall Maria, Deltoff counters that one branch of the military cannot be allowed to have exclusive access to someone as powerful as Eren.
The trial is interrupted by news that Wall Rose has been breached. Deltoff quickly converses with his fellow assembly members, ordering that Wall Sina be sealed against any refugees, expressing concern that allowing refugees inside will create new enemies. He and the other leaders then discuss how there is a silver lining in that they will soon obtain "it." However, they are interrupted by the arrival of Dhalis Zachary who reveals the news of an attack was a ruse and declares them unfit to lead. Deltoff is then arrested and removed from power.
After being overthrown, Deltoff and his comrades are repeatedly tortured by Zachary. Confident that Rod will be able to erase the populace's memories once he has recovered the Coordinate, the nobles do not bother trying to keep anything secret, and freely give away all of the government's secrets.
After Rod Reiss is finally defeated and Historia is crowned as the queen, Deltoff is seen inside a prison.