Zeke Jaeger was the former War Chief of Marley's Warriors, assigned to take the Founding Titan from the Eldians of Paradis Island. He was the current holder of the Beast Titan, and was considered the strongest warrior by Reiner Braun, contrasting Levi Ackermann's title of "humanity's strongest soldier." He manipulated and deceived both sides of the war between Eldia and Marley in order to achieve his own agenda of causing the extinction of his own people, which he viewed as "salvation."
He was the son of Grisha Jaeger and Dina Fritz, older half-brother of Eren Jaeger through his father and a member of the Fritz royal family through his mother.
Appearance: In his human form, Zeke had a tall, broad, well-toned body with blue eyes, shaggy blond hair, and a matching mustache that descended down into his beard. He was seen wearing loose pants with no shirt on, combat boots, and circular glasses. Four years after his return to Marley, Zeke began to sport a more clean-cut look, contrasting his look while on Paradis Island.
History: Zeke Jaeger was born to Grisha Jaeger and Dina Fritz, Restorationists who were planning to overthrow the Marley government and put the Eldians back in power. When the Marley government announced the Warrior program, asking for Eldian children between the ages of five to seven to serve as potential Warriors, Grisha decided to enroll Zeke into the program for the latter to infiltrate the Marleyan military as a spy for the Restorationists. At home, Zeke was routinely sent to his grandparents while both Dina and Grisha attended Eldian Restorationist meetings, with most of his visits being spent listening to his grandfather recounting stories of the Eldian race's crimes against the world.
Story: Five years after the start of the Paradis Island Operation, Zeke travels with Pieck and a small number of Marleyan soldiers to Paradis Island to infiltrate the Walls. After arriving, the group locates a small village inside of Wall Rose, and chooses to turn its residents into Titans. The soldiers releases a gas laced with Zeke's spinal fluid into the air, which is blown into the village and inhaled by the villagers.
Abilities: Zeke was able to transform into a 17-meter Titan referred to as the Beast Titan. He used the Titan when he transformed the inhabitants of Ragako into Titans and impose his will on them. He retained his human mind when transformed, allowing him to do delicate tasks, and he even retained his ability to speak.
Source: Zeke Jaeger (Anime), available under CC BY-SA 3.0.