Monolith
The word Monolith literally means "one stone." In the real world, it refers to geological formations, monuments, and even whole mountains that are made of a single, unbroken stone. Many fictional settings use the word in a similar sense, referring to objects made of a single stone; the implication is that such artifacts were not so much "made" as shaped, suggesting a great deal of dedication on the part of the maker.
In many game settings and works of fiction, artifacts of long-gone civilizations are often Monoliths. The lack of moving parts means that they do not easily break down over time, while simultaneously making them extremely mysterious: without any obvious mechanisms, they must operate on some magic or advanced super-science completely unknown to us.
2001: A Space Odyssey
The iconic monolithic artifact is the Monolith from 2001: A Space Odyssey. In appearance, they are literal black boxes with dimensions in a ratio of 1:4:9 (and so on, in the higher dimensions). Nobody's really sure who made them or why, but they are extremely powerful: a Monolith on Earth sparked the intelligence of the proto-humans living there, and a Monolith orbiting Saturn served as a portal to other Monoliths in the universe, and later turned Jupiter into a star.
Warhammer Fantasy
The various armies of Chaos in the Old World will often leave Monoliths lying around. Some of them are gravestones for a fallen or Spawn-ified hero, others a record of victories or ascension to Daemonhood, and all of them can be (and often are) used as foci for Chaos magic, encampments, and temples.
Warhammer 40,000
In Warhammer 40,000, the Monolith is the Necrons' main tank, capable of teleporting units. AV14 all around, bitch! Unfortunately, the new codex pulled its firepower and versatility down, putting it at about the offensive equivalent of a Leman Russ Battle Tank but with shorter ranges, a deep-strike, and an interesting special ability.
It went through several versions:
- 3E Necron codex: Indestructible, raped all nearby enemies.
- 5E rules: Even more indestructible, same amount of rape.
- 5E Necron codex: Nerfed to Land Raider levels,
but rapes even harder when in assault rangewith inferior special defenses, weakened weapons, and a loss of its failure-free deep strike. - 6E rules: The sixth ed. rules regarding skimmers give it a 5+ jink save, completely destroying any concept of the rules being more realistic, as monoliths can now evade lascannons and shit by doing barrel rolls somehow. Hilarious as it was, it was FAQ'd out in September 2012 (Skimmers that are also Heavy lose the jink special rule - monolith is heavy, man). Overall, see 5E Necron codex status.
- 7E rules: Same as the sixth ed. but with slightly higher resistance to exploding and the added benefit of AV 14 be stronger in general with the rule changes. Not being able to use the new Jink rules is a blessing in disguise because it would leave the Particle Whip unable to fire. The monolith overall received no nerfing this edition for once (actually getting a upgrade in a lot of ways) and with a lot of its competition in the other codexes receiving some downgrades this could be the sign of the big green pyramid making a comeback.