The shadow of Morgoth

For Fëanor, being come to his full might, was filled with a new thought, or it may be that some shadow of foreknowledge came to him of the doom that drew near; and he pondered how the light of the Trees, the glory of the Blessed Realm, might be preserved imperishable. Then he began a long and secret labour, and he summoned all his lore, and his power, and his subtle skill; and at the end of all he made the Silmarils.

J.R.R.Tolkien, "Silmarillion"