Complex sentence: 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.
Split into simpler sentences: It is later revealed that Eren possesses the ability to transform into a 15 meter class Titan. Eren believes this ability to be the result of injections given to him by his father after the death of his mother.