Legend of Grimrock is an old-school dungeon crawler with gameplay similar to Eye of the Beholder, but with more advanced 3D graphics. The player creates a party of up to four characters, assigns them various weapons and armor, and they can also cast spells. Swinging a weapon is handled by clicking on the character's weapon icon which takes a little time to reload before the character can swing again. The game features auto-mapping as the party explores the areas, similar to that of Lands of Lore: The Throne of Chaos, which can be turned off for hardcore players who wish to relive the early years of dungeon crawlers where an auto-mapping feature was not present.
The story focuses on four prisoners who receive a royal pardon, the moment they are thrown into the dungeons of Mount Grimrock. The king hopes that one such group of prisoners will one day conquest the mountain and be able to tell of the secrets of this ancient place, but so far, nobody has come out alive. While trying to escape from the mountain, the party will encounter many tunnels, traps, contraptions and dangerous creatures as they fight for their lives.