Okay, I have this theory about the Titans and how they came to be, and it's the best explanation I've got. I consider this my headcanon until the manga/anime says so otherwise.
The Titans are humans trapped in an endless nightmare, not able to control their bodies, but Ymir transformed back into a human right? And Bertholt, Reiner and Annie were regular titans as well, as far as I believe. I think after that great war that weakened humanity to the titans, a government began to experiment to create a supersoldier. A Titan. Powered by sunlight, an endless energy source. However this Titan could not control himself and was trapped in his titan body, without a way of turning back. In its madness it began to instinctively eat humans and inadvert…Read more >