Chaining of Melkor
From Tolkien Gateway
The Chaining of Melkor refers to his imprisonment for "three ages" after the War for Sake of the Elves. After their final victory in the Siege of Utumno, Tulkas captured Melkor and bound him with the great chain Angainor. He was carried by to Valinor and sentenced to his long term of incarceration by the Elder King and chief of the Valar, Manwë.
During this period (Y.T. 1100 - Y.T. 1400), which is divided in three ages of 100 Valian Years each, the Days of Bliss occurred.
- During the first age, the Elves were able to undertake the Great Journey to Valinor unmolested and the cities of Eldamar were built.
- During the second, many princes of the Elves were born in Eldamar, and Fëanor created the Tengwar.
- During the third, Menegroth was built and the Nandor reached Beleriand.