Linked and yet linked again
bound to be bound for binding
once to hold for great ages three
til one did find himself free.
Angainor
Angainor was the chain forged by Aule to bind Melkor after his first defeat. He was sentenced to remain in the Halls of Mandos until three ages had passed. Later, wen he was again defeated, he was again bound with the chain Angainor (Source: The Silmarillion).
Tolkien Gateway: Angainor