The Crissaegrim were home to the great Eagles of Thorondor. The great Eagles moved to The Crissaegrim after Morgoth's return to Thangorodrim. It was here that Thorondor, the Lord of the Eagles lived, and from here he watched for spies attempting to find the hidden city of Turgon in the vale of the River Sirion. The Crissaegrim formed a part of the southern Echoriath, which were the Encircling Mountains of Gondolin.