Adventure was the granddaddy of all interactive fiction and text adventure games. The mainframe version of Zork was designed as a remake/improvement of that game. Like that, Colossal Adventure was designed as a port/remake of the same parent game, though this time by a British studio (Level 9) rather than MIT engineers.
These games are very much inspired by Tolkein and this was sometimes called the first game in the Middle Earth trilogy. They were later remade with graphics with the Middle Earth references removed and called the Jewels of Darkness trilogy.
Colossal Adventure is a complete, full-size version of the classic mainframe game "Adventure" with all the treasures, creatures, rooms and puzzles of the original. And we have added 70 bonus locations to the end game. No one else gives you this.
Feelies here - http://l9memorial.if-legends.org/html/ca.html
Level 9 Computing went out of business in 1991. To my knowledge, no one owns the copyright to L9 games anymore and they are truly abandonware.