Angband is a roguelike game. It was first intended as a UMoria 5.2.1 variant with more Tolkien Tolkien-inspired content. Angband has seen a lot of changes by a lot of different developers and has been ported to a lot of different platforms. The open nature of the codebase (first under a free for non-commercial purposes license, now under the GNU GPL) has lead to the development of dozens of variants. Angband is still in development and is considered one of the foundations of the roguelike genre.
Angband is a dungeon crawling game. The goal is to travel down to the 100th level and kill Morgoth the Valar (the major villain in Tolkien's "The Silmarillion"). The player chooses between 11 races and 6 classes to create a character, buys equipment from the shops on the surface, and sets off to explore the dungeon, kill monsters and gather loot and experience. Angband features non-permanent levels (if the player leaves level 11 and come back to it later, a new one is generated), randomized objects (a pink potion could be a Potion of Healing in one game and a Potion of Confusion in the next), hundreds of different monsters and powerful Unique creatures and artifacts from Tolkien mythology (Sauron, Saruman, Grishnakh the Orc, Elendil...).
Angband has several display modes (ASCII text or graphical tiles), as well as a sound engine in recent releases.
Angband can be freely downloaded at the Angband homepage: http://rephial.org/.