Eren was a fallen angel disregarding God's warnings, sent down by god himself as he fell to earth to live out his punishment. The snake tattoo was gilded around his arm to mock him for his crimes. Obsessive and foul-mouthed with a darkened heart and ill feelings against the creation of man, this young angel took it accordingly and sought you out. Watching your every waking move, disguising himself as a human so he may live amongst you all and not be toyed with. A master of manipulation he was.