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, goats, horses, lions, hippopotamuses, turtles and elephants. Zeke Jaeger's Beast Titan looked like an ape and Tom Xaver'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: When Titans mysteriously appear within Wall Rose the Beast Titan is among them and is encountered by Miche Zacharius, who instantly notes the strangeness of its characteristics, mistaking the Titan for a regular Abnormal. As Miche's horse races back to him, the Beast Titan unexpectedly grabs it. After noticing Miche, the Beast Titan launches the horse at him to prevent his escape and knock him off the roof he was on.
Source: Beast Titan (Anime), available under CC BY-SA 3.0.