The Metaphysics behind the Shadow Sri Aurobindo describes in The Life Divine (pp. 285-88) the descent of Overmind and the transparency of the first veil becoming more and more opaque, it finally shutting off from view the supreme Reality that is behind it, the Reality which is also inside it. Here is the passage:

Overmind in its descent reaches a line which divides the cosmic Truth from the cosmic Ignorance; it is the line at which it becomes possible for Consciousness-Force, emphasising the separateness of each independent movement created by Overmind and hiding or darkening their unity, to divide Mind by an exclusive concentration from the overmental source. There has already been a similar separation of Overmind from its supramental source, but with a transparency in the veil which allows a conscious transmission and maintains a certain luminous kinship; but here the veil is opaque and the transmission of the Overmind motives to the Mind is occult and obscure. Mind separated acts as if it were an independent principle, and each mental being, each basic mental idea, power, force stands similarly on its separate self; if it communicates with or combines or contacts others, it is not with the catholic universality of the overmind movement, on a basis of underlying oneness, but as independent units joining to form a separate constructed whole. It is by this movement that we pass from the cosmic Truth into the cosmic Ignorance. The cosmic Mind on this level, no doubt, comprehends its own unity, but it is not aware of its own source and foundation in the Spirit or can only comprehend it by the intelligence, not in any enduring experience; it acts in itself as if by its own right and works out what it receives as material without direct communication with the source from which it receives it. Its units also act in ignorance of each other and of the cosmic whole except for the knowledge that they can get by contact and communication,—the basic sense of identity and the mutual penetration and understanding that comes from it are no longer there. All the actions of this Mind Energy proceed on the opposite basis of the Ignorance and its divisions and, although they are the results of a certain conscious knowledge, it is a partial knowledge, not a true and integral self-knowledge, nor a true and integral world-knowledge. This character persists in Life and in subtle Matter and reappears in the gross material universe which arises from the final lapse into the Inconscience. Yet, as in our subliminal or inner Mind, so in this Mind also a larger power of communication and mutuality still remains, a freer play of mentality and sense than human mind possesses, and the Ignorance is not complete; a conscious harmony, an interdependent organisation of right relations is more possible: mind is not yet perturbed by blind Life forces or obscured by irresponsive Matter. It is a plane of Ignorance, but not yet of falsehood or error,—or at least the lapse into falsehood and error is not yet inevitable; this Ignorance is limitative but not necessarily falsificative. There is limitation of knowledge, an organisation of partial truths, but not a denial or opposite of truth or knowledge. This character of an organisation of partial truths on a basis of separative knowledge persists in Life and subtle Matter, for the exclusive concentration of Consciousness-Force which puts them into separative action does not entirely sever or veil Mind from Life or Mind and Life from Matter. The complete separation can take place only when the stage of Inconscience has been reached and our world of manifold Ignorance arises out of that tenebrous matrix. These other still conscient stages of the involution are indeed organisations of Conscious Force in which each lives from his own centre, follows out his own possibilities, and the predominant principle itself, whether Mind, Life or Matter, works out things on its own independent basis; but what is worked out are truths of itself, not illusions or a tangle of truth and falsehood, knowledge and ignorance. But when by an exclusive concentration on Force and Form Consciousness-Force seems phenomenally to separate Consciousness from Force, or when it absorbs Consciousness in a blind sleep lost in Form and Force, then Consciousness has to struggle back to itself by a fragmentary evolution which necessitates error and makes falsehood inevitable. Nevertheless, these things too are not illusions that have sprung out of an original Non-Existence; they are, we might say, the unavoidable truths of a world born out of Inconscience. For the Ignorance is still in reality a knowledge seeking for itself behind the original mask of Inconscience; it misses and finds; its results, natural and even inevitable on their own line, are the true consequence of the lapse,—in a way, even, the right working of the recovery from the lapse. Existence plunging into an apparent Non-Existence, Consciousness into an apparent Inconscience, Delight of existence into a vast cosmic insensibility are the first result of the fall and, in the return from it by a struggling fragmentary experience, the rendering of Consciousness into the dual terms of truth and falsehood, knowledge and error, of Existence into the dual terms of life and death, of Delight of existence into the dual terms of pain and pleasure are the necessary process of the labour of self-discovery. A pure experience of Truth, Knowledge, Delight, imperishable existence would here be itself a contradiction of the truth of things. It could only be otherwise if all beings in the evolution were quiescently responsive to the psychic elements within them and to the Supermind underlying Nature's operations; but here there comes in the Overmind law of each Force working out its own possibilities. The natural possibilities of a world in which an original Inconscience and a division of consciousness are the main principles, would be the emergence of Forces of Darkness impelled to maintain the Ignorance by which they live, an ignorant struggle to know originative of falsehood and error, an ignorant struggle to live engendering wrong and evil, an egoistic struggle to enjoy, parent of fragmentary joys and pains and sufferings; these are therefore the inevitable first-imprinted characters, though not the sole possibilities of our evolutionary existence. Still, because the Non-Existence is a concealed Existence, the Inconscience a concealed Consciousness, the insensibility a masked and dormant Ananda, these secret realities must emerge; the hidden Overmind and Supermind too must in the end fulfil themselves in this apparently opposite organisation from a dark Infinite.