Chaos was the predominant force in the cosmos, and it influenced the other Spheres of Time, Matter, Energy and Thought. The opposing force at the time was the Sphere of Life, sometimes called the Sphere of Integration or, as Sharon put it, the Sphere of Stasis. These events did not necessarily happen in that sequence, but they all did happen. Thus, ending the Age of Chaos, and beginning of the Age of Order. In the present state of the cosmos, things are reversed.
Fear is the key.
I propose that the ND are remnants of the old Age of Chaos, when Entropy reigned and the 4 Spheres belonged to Chaos. Hence, the Chaotic Seed of the Negative Sphere of Energy is hidden in the Sphere of Thought. The Immortal might not have been fully aware of the true nature of the Chaotic Seed, and only saw Blackflame as a direct opposition of Energy, and therefore, helpful to the objectives of Thought. The discovery of the Blackflame might be a portent or an ushering of another Age of Chaos. Not even the Immortals know this.