The Silmarillion

Then Ulmo answered: 'Truly, Water is become now fairer than my heart imagined, neither had my secret thought conceived the snowflake, nor in all my music was contained the falling of the rain. I will seek Manwë, that he and I may make melodies for ever to my delight!' And Manwë and Ulmo have from the beginning been allied, and in all things have served most faithfully the purpose of Ilúvatar.

But even as Ulmo spoke, and while the Ainur were yet gazing upon this vision, it was taken away and hidden from their sight; and it seemed to them that in that moment they perceived a new thing, Darkness, which they had not known before except in thought. But they had become enamoured of the beauty of the vision and engrossed in the unfolding of the World which came there to being, and their minds were filled with it; for the history was incomplete and the circles of time not full-wrought when the vision was taken away. And some have said that the vision ceased ere the fulfilment of the Dominion of Men and the fading of the Firstborn; wherefore, though the Music is over all, the Valar have not seen as with sight the Later Ages or the ending of the World.

Then there was unrest among the Ainur; but Ilúvatar called to them, and said: 'I know the desire of your minds that what ye have seen should verily be, not only in your thought, but even as ye yourselves are, and yet other. Therefore I say: Eä! Let these things Be! And I will send forth into the Void the Flame Imperishable, and it shall be at the heart of the World, and the World shall Be; and those of you that will may go down into it. And suddenly the Ainur saw afar off a light, as it were a cloud with a living heart of flame; and they knew that this was no vision only, but that Ilúvatar had made a new thing: Eä, the World that Is.

Thus it came to pass that of the Ainur some abode still with Ilúvatar beyond the confines of the World; but others, and among them many of the greatest and most fair, took the leave of Ilúvatar and descended into it. But this condition Ilúvatar made, or it is the necessity of their love, that their power should thenceforward be contained and bounded in the World, to be within it for ever, until it is complete, so that they are its life and it is theirs. And therefore they are named the Valar, the Powers of the World.

But when the Valar entered into Eä they were at first astounded and at a loss, for it was as if naught was yet made which they had seen in vision, and all was but on point to begin and yet unshaped, and it was dark. For the Great Music had been but the growth and flowering of thought in the Tuneless Halls, and the Vision only a foreshowing; but now they had entered in at the beginning of Time, and the Valar perceived that the World had been but foreshadowed and foresung, and they must achieve it. So began their great labours in wastes unmeasured and unexplored, and in ages uncounted and forgotten, until in the Deeps of Time and in the midst of the vast halls of Eä there came to be that hour and that place where was made the habitation of the Children of Ilúvatar. And in this work the chief part was taken by Manwë and Aulë and Ulmo; but Melkor too was there from the first, and he meddled in all that was done, turning it if he might to his own desires and purposes; and he kindled great fires. When therefore Earth was yet young and full of flame Melkor coveted it, and he said to the other Valar: 'This shall be my own kingdom; and I name it unto myself!'

But Manwë was the brother of Melkor in the mind of Ilúvatar, and he was the chief instrument of the second theme that Ilúvatar had raised up against the discord of Melkor; and he called unto himself many spirits both greater and less, and they came down into the fields of Arda and aided Manwë, lest Melkor should hinder the fulfilment of their labour for ever, and Earth should wither ere it flowered. And Manwë said unto Melkor: 'This kingdom thou shalt not take for thine own, wrongfully, for many others have laboured here do less than thou.' And there was strife between Melkor and the other Valar; and for that time Melkor withdrew and departed to other regions and did there what he would; but he did not put the desire of the Kingdom of Arda from his heart.