The Doom of Mandos, also called the Doom of the Ñoldor, the Curse of Mandos or the Prophecy of the North, was the judgement of the Valar pronounced on the elves that carried out the Kinslaying at Alqualondë:

"Tears unnumbered ye shall shed; and the Valar will fence Valinor against you, and shut you out, so that not even the echo of your lamentation shall pass over the mountains. On the House of Fëanor the wrath of the Valar lieth from the West unto the uttermost East, and upon all that will follow them it shall be laid also. Their Oath shall drive them, and yet betray them, and ever snatch away the very treasures that they have sworn to pursue. To evil end shall all things turn that they begin well; and by treason of kin unto kin, and the fear of treason, shall this come to pass. The Dispossessed shall they be for ever. ..."

The Kinslaying was the elves' equivalent of man's Original Sin, in that they fell to evil and were expelled from paradise.

The pronunciation of this Doom was the immediate cause for the return to Valinor of (already reluctant to proceed) Finarfin and his followers. There they asked and received the forgiveness of the Valar.