Some TMNT stuff really isn't for little kids.
Dreamer and Dragon were created from Brahma as dual aspects of his personality - Dreamer to mantain, and Dragon to destroy - operating within his creation. The siblings grew isolated from their father's omniscience, and thus unable to know his plans. To understand him better as a creator, they became creators, themselves. Dreamer gave life to birth, and Dragon gave into hunger. The two learned while they worked, but Dragon was never satisfied. In an attempt to ease Dragon's nonconformity, she helped him design a Pantheon of demigods wise and powerful enough to manipulate and intervene in the settlement of creation.
Dreamer, however, needed to be more. To replicate Brahma's divine concept, she had to become one with this universe, as he was one with the multiverse. Thus, she reverted to an infant form inside a tree within the afterlife, dreaming and living through the lives of a new creature called the "human". Unfortunately, Dragon could not accept this and infiltrated her dreams, influencing mankind to perform the most terrible deeds of their history - her nightmares.
In order to stop Dragon, Dreamer designed a mortal soul as a prison for him, binding him to the same cycle of death and rebirth that all living beings suffer - the soul of Oroku Saki. But Kitsune, one of the Pantheon, never lost track of her father and had a plan to bring him back, and to bend Saki to her will, he needed to be able to love and trust her. This was difficult for her, for she had actually fallen in love with the mortal, herself.
Whilst in Hell, Saki watched his once and again friends Hamato Yoshi and Tang Shen return to a state in which they were to be reincarnated. Just then, the tree in front of him burst open, revealing the massive infant form of Dreamer. She returned to her normal form and told him that humans need to forget themselves in order to know of their true selves, but because he has always shared existence with The Dragon, he must first know of her and her brother.