Titans were a species of giant man-eating humanoids that served as the catalyst for the events in the Attack on Titan series. The people inside the Walls were taught that they first appeared 107 years prior to year 850 and rapidly exterminated humanity to the point of near-extinction. In reality, they were transformed humans known as Subjects of Ymir and had existed for nearly 2,000 years. However, after Eren Yeager's death and Ymir's decision to relinquish her power, all the Titans returned to their human forms, thereby rendering the species nonexistent.
Appearance: Titans strongly resembled nude humans. ). The vast majority of Titans had exceptionally wide mouths with an array of entirely sharp (in certain instances), or entirely flat teeth (which was more common in most observed titans).
History: Around 2,000 years ago, a slave named Ymir discovered a large tree while fleeing from her masters, the Eldians. The tree had an entrance that led to a pit full of water. Unaware of the water, Ymir entered the tree and immediately fell into the pit.
Trivia: Despite their English name originating from the of , the Titans of Attack on Titan are much more influenced by the of . " Some Titans are modeled after friends and acquaintances of Hajime Isayama. Sometimes, he will even take requests.
Source: Titan, available under CC BY-SA 3.0.