De Marigny's Clock is an artefact of the Elder Gods which appears in Brian Lumley's Titus Crow series of Cthulhu Mythos novels and short stories. It was inspired by a line written by H. P. Lovecraft and E. Hoffman Price in the short story Through the Gates of the Silver Key.
Disguised as a grandfather clock shaped like a coffin, the Clock is in fact an incredibly advanced ship with the ability to traverse time, space and, with the correct pilot, dimensions as well. It features a door on the front body which is large enough to admit a full-grown human. Upon stepping inside, pilot and passengers will become enveloped in a white mist which cushions their bodies perfectly, presumably to protect them from any manoeuvring stresses.
Controlling the Clock's direction of travel - either in the material universe or through time - requires nothing more than the mental concentration of the pilot, who may use the advanced sensors to view his surroundings out to a tremendous distance. It is capable of travelling at faster than light speed both in and out of an atmosphere (although it features inbuilt safeguards to prevent most collisions), is capable of moving through time at the speed of thought, and can be outfitted with a variety of sensor and weapon packages depending on the requirements of the user. As a device created by the Elder Gods, the weapon systems are powerful enough to physically harm, if perhaps not destroy, entities as powerful as a Great Old One, as seen when Titus Crow used the Clock's energy beam against Ithaqua.