The Beast Titan was one of the Nine Titans. Typically, it was slightly larger than most Titans and took on an animal-like appearance.
Abilities: Unlike the majority of other Titans, which retained a largely "human" appearance, the Beast Titan exhibited animal-like traits, which greatly varied depending on its holders: some of the various animal appearances shown from prior holders of the Beast Titan have included monkeys, birds, crocodiles, elk, bulls, wolves, snakes, rabbits, dinosaurs, okapis and goats. Zeke Yeager's Beast Titan looked like an ape and Tom Ksaver's contained traits found in bighorn sheep, while Falco Grice testifies that there once existed a Beast Titan with wings. Furthermore, Zeke's spinal fluid, which carried the power of the Beast Titan, was used to transform Falco into a Titan and evidently gave his Jaw Titan falcon-like characteristics similar to those of a Beast Titan.
History: The Beast Titan, like all the Nine Titans, was brought into the world after the death of Ymir Fritz. In the 1,700 years following her death, the Beast Titan was held in the possession of one or several of the warring Eldian houses subservient to the Founding Titan. After these seventeen centuries, when Karl Fritz, the 145th King of the Fritz family, abandoned the conflicts of Eldia and relocated to Paradis Island, the Beast Titan was taken by the nation of Marley during the Great Titan War.
Story: In the year 850, Zeke Yeager infiltrates Wall Rose and uses the power of his Beast Titan to transform the residents of Ragako into Titans, possibly as a way to test the strength of the Eldians within the Walls. Shortly afterward, a small group of his Titans is spotted by Squad Leader Mike Zacharias, who begins a mission with fellow soldiers and recruits of the Survey Corps in spreading the news of a Wall Rose invasion. After killing five of Zeke's Ragako Titans, Zeke takes Mike's horse and throws it his way, sending him falling into the mouth of a Titan.
Trivia: The Beast Titan is ranked 3rd on the Titan Popularity Poll. Zeke's Beast Titan's appearance resembled several , such as "Bigfoot," the Yeti, and Yowie. The eyes of Zeke's Beast Titan originally had white sclerae with human-like irises and pupils; however, they later got changed to having black sclerae with a large light dot in the center.
Source: Beast Titan, available under CC BY-SA 3.0.