Rod Reiss is an antagonist in Attack on Titan, serving as the main antagonist of the Uprising Arc, and the father of Historia Reiss, formerly known as "Krista Lenz". He is the real King of the Walls and uses a false royal family under a false puppet, presented as the Fritz family, to hide his true power. He is also the true reason why the Military Police Brigade wanted Eren Yeager so badly during the Female Titan arc, making him the unseen secondary antagonist of the arc.
He is a member of the royal family of direct descendants of Ymir Fritz, the very first Titan in history and goddess queen. When the First King of the Walls erased the memories of the caged humanity, the Fritz family changed their name in Reiss to hide their origins.
Rod was the eldest son of Mr. Reiss, the holder of the mysterious Coordinate at the time. Some time later, he was joined by a younger brother, Uri. Uri and Rod constantly begged their father to release humanity from their encagement, but he always refused, never disclosing why. It apparently had been so many times that Rod was locked behind bars for his attempts, and it is implied to have happened more than once. When it came time for his father to pass his position to a son, Uri volunteered, asking Rod to pray. After Rod observed his father's presence in Uri the moment his brother had opened his eyes, he realized he had become an all-knowing being and protector of the world; God. On his brother's promise, Rod had devoted his time to protecting God and offering his prayers to it.
When Rod was still a young boy, he met Kenny Ackerman when he tried to kill his brother and former king, Uri Reiss. Despite Rod telling Uri several times that they should kill him, especially if he was an Ackerman, Uri refused and apologized to Kenny. This created a bond between the two and Kenny became a servant of the Royal Family, especially to Rod. Sometime after this, Rod married an unnamed woman and had five children with her: Frieda; Ulkin; Dirk; Abel; and Florian.
Rod Reiss conceived Historia with Alma, one of his maids. When Historia was discovered, his mistress and daughter were exiled to a land that he leased to Historia's maternal grandparents.
On the day that Wall Maria fell to the Armored and Colossal Titan's attack, the entire Reiss family went to a chapel to pray in a secret underground area. However, somehow Grisha Jaeger appeared and engaged Frieda Reiss in combat. Though Frieda possessed the powers of the Coordinate, she was eaten by Grisha. Grisha then proceeded to kill the rest of the Reiss bloodline, even the children, with only Rod escaping, blindly fleeing as his family was killed.
Rod is seen with Kenny Ackerman in the Reiss underground chamber. He unlocks Eren's lost memories of being transformed into a Titan and devouring his father, Grisha. He also remembers what his father did, as the memories of the Reiss massacre come pouring back to him.
Rod states that he can't become a shifter, whether due to blood or choice is unknown. He tries to convince his daughter Historia to eat Eren and become a God like her uncle Uri had become.
Though she nearly does it, she throw the syringe down at the last moment, freeing Eren. An emotional unstable Rod Reiss then attempts to lick the serum off the ground, and begins to transform into a Titan.
The now enormous Rod Reiss begins to crawl towards the Orvud District, where the steam generated from his body would destroy the District. At dawn, the Garrison and Survey Corps begin their assault as the manage to blow off his head and nape. The final blow is committed by his bastard daughter, Historia, as she slices his human nape.