Angband was a mighty fortified citadel originally constructed by Morgoth (Melkor) in the earliest days of the world as an outlying fortress to his northern stronghold of Utumno. Utumno was destroyed by the Valar, and Morgoth imprisoned in Valinor for three ages, but on his return to Middle-earth, he took Angband as the seat of his power, and raised the towers of Thangorodrim above its gates.
Angband was besieged by the Noldor during the early part of the First Age, but the Siege of Angband was broken at the Dagor Bragollach. It was finally destroyed by the forces of the Valar at the end of the First Age, in the War of the Wrath.
It's a freeware computer dungeon exploration game based (loosely) on the books of J.R.R.Tolkien. You explore a very deep dungeon, kill monsters, try to equip yourself with the best weapons and armor you can find, and finally face Morgoth - "The Dark Enemy".