The Heroes Of Karn is a 1983 adventure game written by Ian Gray with music by Chris Cox.
The player must rescue four heroes who have been magically imprisoned, and thus save the land of Karn from dominion by evil creatures. The heroes are Beren the swordsman, Istar the wizard, Haldir the Elf-lord, and Khadim the dwarf.
The game's parser accepts standard four-word sentences (e.g. "kill troll with axe"). The puzzles are mostly straightforward, involving the use of an object found elsewhere to defeat the creature that is impeding progress. The creatures and NPCs in the game, including the heroes themselves, are rather inert and are very limited in their interactions.
The game is mostly text, with illustrations for some of the locations. The Commodore 64 version of the game received criticism for slow loading of graphical scenes, which could take as long as several minutes to display completely. The Spectrum and Amstrad CPC versions were by a different artist (Tony Greer) and quicker to draw.
A sequel, The Empire Of Karn, was released in 1985 on the Commodore 64.
Source: Wikipedia, "Heroes Of Karn", available under the CC-BY-SA License.