Leeries

Even though they are located underground, The Tree layers of The Pit have their cycle of day and night thanks to the glow emitted by The Tree. Like a steady breath, the glow gains intensity and dims over the passing hours. Over the season of Dream, when The Tree goes to "sleep", its glow is the weakest, turning the normally well-lit places dangerous when not traversed with some source of light or even completely pitch-black. The glow of The Tree also has an additional property that scares away most of the bigger and more dangerous creatures from the center of The Pit.
And so, the system which would light up many areas around The Tree layers had to either be strong enough to withstand any possible damage caused by the monsters that would show up during darker seasons or be portable/automated enough to be hidden when a danger would appear. The company that produces mostly robotic homunculi, Walking Cogs, Inc. offered its solution to this problem.
They created Leeries, a modern mobile lighting system of homunculi with the functionality of assessing danger, communication between units, and warning about threats.

Functions

Leeries' main function is to serve as streetlights during the night and in some darker parts of Tree layers, though places that are always dark would be too power-consuming for them to function for long.
While there have been a few different models in the past, most are divided into two types depending on their function.

Candles

The candles serve as transmitters, power banks, and controllers of all the streetlight leeries in the area. First, they regularly check on their "coworkers" both through the radio transmissions and by visiting them. Should anything happen to other Leeries under them, it is their job to inform someone, either a member of a maintenance team or someone in charge in the area. Should no one like that be in the area, it is their job to seek out someone who could repair their brethren but only after enough units malfunction.
Second, candles transmit the information from one streetlight to another one. These are mostly messages about the danger in the area, Should they mention any possible threat to humans, the candles will coordinate the operation to cordon off the area by placing blinking streetlights, and should it be safe, to play the announcements warning the approaching people of the danger.
Lastly, the candles "wake up" all the other Leeries should the light level in the surrounding area drop too much by charging them up with either Light, Fire or Electric Elemental Crystals, stored within their cases. They also check up on the others to see if they still have enough charge for them to function normally during the night.

Streetlights

The streetlight's main function is to bring light to the area, although that is not the only thing they can do. Normally, Light Crystals only give off a pure white light, but Leeries are one of the few creatures capable of changing it without the need for anything like colorful stained glass or transparent materials. They use that ability to give off different signals and warnings, usually shifting the color of the Light more to the red the more dangerous threats are in the area. If it won't bring danger to the humans close by or to them, the Leeries will play one of many announcements that might specify what kind of danger one could expect.

Power source

The Leeries operate using the power of Elemental Crystals. They can uphold their designated functions for up to one week of continuous work without charging. They can also use the same power source as well as the reserve one just for movement. If their designated functions are used sparingly, they potentially could drive around The Pit for about 90 days, shorter if they end up going through rougher terrain.

Appearance

In their inactive state, Leeries look like metal suitcases with tracked treads on their sides. When activated, they transform between a flatter, horizontal position, better suited for movement, and a vertical position intended for work. All Leeries have one long, extendable metal arm they use either as lanterns, to manipulate the objects in their surrounding, or even for movement since the pistons controlling the arm are strong enough to pull and support their weight.
To make them look more friendly, the creator of Leeries gave them four long narrow lights, two on each of the two sides facing forward during their two modes of operation. The lights simulate the blinking of the eyes. They are completely cosmetic and serve no sensory purpose.
Here are a few differences between the two types of Leeries.

Candles

• Bulkier, bigger case, designed to store multiple Elemental crystals within.
• Longer arm, serving also as an antenna.
• Multiple lenses, giving Leerie full vision all around them.

Streetlights

• Leaner, more elegant case.
• Shorter arm with a fuller range of motions.
• Single lens with a big cone of sight

Perception and Sensors

Leeries have multiple different ways to detect their surroundings. First, they have a similar range of vision to that of humans, giving them the ability to notice places that are too dark to comfortably go through. Additionally, their lenses are equipped with thermal vision and motion detection systems. They are also equipped with systems that detect vibrations of the ground beneath them, gas and radiation detectors, and even detectors that let them check the purity of the water. More than all that, Leeries possess enough sapience to recognize threats similarly to humans and other living beings.
It is important to remember that Leeries do not perceive humans as a threat, so even if they give off no warnings about dangerous beings in the area, it doesn't mean that the place is safe. Leeries can be met even inside the bandit camps. Even there, they will follow their main function to bring light and warn humans about danger nearby.

Genetic Ancestor(s)

• Homunculus

Average Weight

1 meter, around 3 meters with the arm holding the light extended.

Geographic Distribution

• The Pit

Speed of movement:

Leeries can maintain a speed of 8 km/h on flat, hard, solid surfaces. When it comes to swimming, only a few models of Leeries are capable of swimming. Most of the others will simply drown. Prolonged submersion is ill-advised as it can pretty quickly destroy the internal components of the Leerie.

Reproduction:

As homunculi, Leeries are incapable of reproduction. The only way for more of them to be there is to either create one of them or produce more of them at the factory.

Dietary needs and charging:

Leeries don't have to eat and can't simulate it due to the lack of anything resembling a mouth on them. They do, however, need to charge up. To charge a Leerie, either an Electric Elemental Crystal or an electric current that will charge the Crystal already within the homunculi is needed. Similarly, the lights they shine need to be either charged with another Light or Fire Elemental Crystal or be exposed to enough light that the Crystal within them absorbs it. The candle Leeries tend to carry multiple units of both of the Crystals needed and are capable of charging multiple of their brethren as long as they all stay close enough for the fun to continue. With a steady power source, Leeries can completely charge up from zero in less than 2 hours.

Distribution:

Leeries can be mainly encountered all around the Tree layers of The Pit. The constantly present sunlight of The Surface layers means they aren't needed there, while all the attempts to use them to light up The Depths have met with failure. Sooner or later, the Beasts dwelling in the darkness would hunt down the Leeries, not giving them any chance to escape.

Language of Leeries

It turns out that Leeries are smart enough to form a basic form of speech using the prerecorded danger announcements within their memory banks. While there are many words they aren't capable of speaking, it is impressive how much they recreated. But what is even more impressive is that using light signals of different colors and the gestures made using their hands, the Leeries created their own language. It hasn't been deciphered completely but from the fragments that have been, it turns out that the Leeries have different personalities, like to gossip about various stuff, and even warn and teach each other how to deal with various threats and obstacles.

One curious light

There is a story of a Leerie that fell down the main shaft of The Pit and landed far below on one of the layers of The Depths. Somehow, it managed to not only survive that fall (technically giving it a title of Pit-leaper) but for the next 85 days it managed to survive, avoiding the attention of the Beasts living in the Depths and climb out of them. While traveling on the "vapors" of its power source, it managed to get close enough to an inhabited settlement that it was picked up and charged up again. Before the called maintenance team managed to get down there, it left the settlement, going back to its brethren. The details of the journey are blurry and people telling this story tend to exaggerate it a lot, but after many adventures on the way, it finally came back to its original group.