It is later revealed that Eren possesses the ability to transform into a 15 meter class Titan, believing this ability to be the result of injections given to him by his father after the death of his mother.
Eren possesses the ability to transform into a 15 meter class Titan, believing this ability to be the result of injections. This was what it is later revealed. These injections are given to him by his father after the death of his mother.