A Grandfather of the so-called "Dungeon crawl" genre, Avalon Hill's Telengard was designed in 1982 by Daniel Lawrence, based on an earlier mainframe game written on PLATO by Gary Whisenhunt and Ray Wood called dnd.
Telengard features a huge 50-level/2-million room dungeon, battle with twenty different types of randomly-generated monsters, and thirty-six unique spells that players can cast. Among other things, there are fountains to drink from with varying results, a jeweled throne to sit upon, an altar to donate gold upon, a strange multicolored treasure box, and a misty teleport cube. Magic weapons, armor, scrolls, and potions were available to those who could find them.
Telengard's earliest known commercial release was 1982, for the TRS-80. Its most popular incarnation, however, was via the Commodore 64, released c.1984.
More on [ Telengard ]

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Balrog - Telengard - Feature list, screenshots, and brief developer commentary.
Telengard Remake - Nostalgic port to Microsoft Windows. Changelog and executable download.
The Telengard Tavern Generator - Humorous auto-generated names derived from TRS-80 version.