SPOILER
Isaac approaches the Marker when the Nicole vision suddenly pulls Isaac into his own mind. There, Isaac encounters the parts affected by the Marker and the Nicole vision, who then reveals that the only way to be "reborn" is to absorb the body and mind of the one who created it. After a lengthy battle, Isaac is able to destroy the Nicole vision and rid all traces of the Marker's influence from his mind, destroying the Marker in the process