Planejammer Campaign Setting
Scattered throughout the Land of the Lost, often embedded in the walls of caverns and some pillars, are a variety of colourful brightly glowing crystals that the Marshalls dubbed “light crystals” and which Enik called “fourth-dimensional nodes.” Sizes vary from boulder-sized chunks to the more common walnut-sized gems (which themselves are merely chunks off the larger crystals) and apparently were artificially grown or otherwise constructed by the Altrusians for use as a power source for their technologies. The larger crystals are possibly mildly radioactive and give off both heat and light as a byproduct of their nature. Rick Marshall theorized that they might even power the dimensional doorways.
Their most common colors are red, blue, yellow, and green, though other rarer colors, such as white, have been seen or mentioned.
In one episode, Rick Marshall laments the number of possible combinations of crystals. In fact, there are 6 possible combinations of 4 colors taken 2 at a time, and 4 possible combinations of 4 colors taken 3 at a time. The crystal matrix tables provide a 9×9 array, which would be capable of storing 162 bits (an astronomical number of possible states) if filled with crystals of 4 distinct colors.
The most common use of light crystals seems to be in crystal matrix control tables, or simply as sources of illumination. On their own, the smaller crystals generally do not have special properties beyond their glow, but bringing two different-colored crystals together can cause additional effects in some cases:
Bringing a red crystal together with a green one causes the pair to emit a blindingly bright but generally short-lived light (Holly used this pair for sustained light in “Elsewhen”); this combination is often useful for driving away Sleestak.
Bringing red and yellow crystals together causes an explosion after a very brief delay.
Putting two green crystals together (or possibly two like-colored crystals) is also an explosive combination.
Combining red and blue do nothing noticeable, but adding a third, yellow crystal to the pair causes them to emit a near-lethal shock.
In general, yellow crystals appear to trigger releases of energy from other crystals.
A blue crystal and a green crystal together create a temporary force field a short distance away. This use was taught to the Marshalls by Enik in “The Stranger”, but in the later episode “The Search”, the Marshalls attempted to reproduce the effect and nothing happened (it’s possible the crystals were dead).
In general, blue crystals appear involved in telepathic functions. Blue crystals alone can under some circumstances hypnotize people into seeing what they love most.8 Jefferson Collie also mentioned that blue crystals “make you sick”, and discards them when he mines them in his cave. The Marshalls eventually receive a set of pendants from Rani – Holly’s future self -with a number of tiny yellow crystals surrounding a larger central blue crystal that provide a sort of clairvoyance, in which one wearer can see what the other wearer is seeing and hear what they’re hearing. Rani explains that the blue crystals pick up the wearer’s heartbeat and transmits empathic signals that are received by the other pendants. In the Series Bible, blue crystals are said to have recording properties and can both record and play back “memories”)
David Gerrold, in his DVD commentary to the episode “Circle”, noted that the idea for the crystals was picked up from Harlan Ellison, who had wanted to use them in his Star Trek episode “The City on the Edge of Forever” but was blocked from doing so.