- How did Titans get inside the wall?
- Are the Titans in the walls human?
- Why did Eren release the wall Titans?
- Why can’t sunlight touch the Titan in the wall?
- Why did killing Zeke stop rumbling?
- Why is Eren evil?
Colossus titans (NOT TO BE CONFUSED WITH THE COLOSSAL TITAN) are the ones used to build the walls through the power of the Founding Titan and their skin is used as the material. They are alive but highly weakened due to the lack of sunlight. The Nine Titans are the fragments of Ymir’s (the Founding Titan) soul.
Despite being Pure Titans, none of the Wall Titans were seen reverting back into human form after the power of the Titans was sealed.
With the full power of the Founding Titan, Eren telepathically declared his will to all Subjects of Ymir that he had unleashed the Wall Titans upon the world to crush all life beyond Paradis Island.
If the sunlight got through it could give enough energy for the titans inside the walls to move. To prevent this from happening the titans are kept in darkness.
The rumbling was caused by the Founder Titan which in possession of Eren, But Eren could not use its Abilities as he was not of royal blood, he was only able to start the Rumbling in coming in contact with Zeke who was of royal blood. Thus killing Zeke cut Eren’s connection to the Founder which stopped the Rumbling.
Similar to witnessing Carla’s death, seeing his friends die caused Eren a lot of pain, resulting in him becoming an antagonist. The more friends he lost, the darker Eren became, until he would have let all of his friends die if it meant killing his enemies.