|A planet of awesome size, lit by no sun. An invisible titan, all thick, black forests and jagged mountains and deep, turbulent oceans.|
|— Cecil Palmer|
The dark planet is an enormous planet that is frequently seen in visions by the citizens of Night Vale. It is not currently known whether or not the planet exists in our or any reality or if it is merely a hallucination. Cecil Palmer describes the dark planet as "a planet of awesome size, lit by no sun, an invisible titan, all thick black forests and jagged mountains and deep, turbulent oceans." Although the descriptions of the dark planet are frightening, those who see it in visions are typically mesmerized by it, with Cecil even describing it as a vision of perfection.
The dark planet is inhabited by mysterious, shrouded figures, who have been seen standing in a circle on a beach, gently swaying into one another before the backdrop of the dark planet's roiling, bottomless ocean.
In episode 146, Lee Marvin mentions that the dark planet has sand, and that he believes that it smells like "the salt tang of invisible oceans... the bitter sap of ancient forest... [not] of rot [or] fire or a food... it smells empty like a home that you lived in for many years but have cleaned out and painted, and are standing in it for the last time and it is once again a stranger to you".
Visions of the dark planet
It is not known what brings about visions of the dark planet, or what it truly is, though it seems to be associated with an approaching death or other form of terrible harm. After Night Vale's Post Office was reopened in February of 2013, visitors reported being psychically assaulted with "visions of strange jagged peaks and a churning black ocean," apparently belonging to the dark planet.
You, the character, also frequently experienced visions of the dark planet, at one point feeling that the planet was so close above that You could almost reach out and touch it. When You reach your hand, the episode ends, and while it is not known what happened to you, you probably died, or were killed by Them.
Cecil Palmer has experienced visions of the dark planet on several occasions. When he was a teenager, while recording himself speaking to prepare for his future as a radio host, he was recorded saying, "I think the radio station is fun. I think the radio station is... hidden. I think the radio station is like a dark planet lit by no sun. I think, therefore I soon won't be." Cecil's vision was immediately followed by some unknown yet horrifying event.
A man who was not short experienced visions of the dark planet that were very similar to the ones that You experienced, and, when he attempted to reach out and touch the planet, he mysteriously died, ceased to exist, or was murdered at that moment by a man who was not tall, who briefly mourned his old partner before climbing into a car with a new man who was also not short. However, this was probably the same thing that happened to You when You tried reaching the planet.
Lusia Tereshchenko saw the dark planet just before, or perhaps just as, she died in 1843. This was in the midst of an operation of the Sheriff's Secret Police, who confronted the men Lucia worked with. The men were unloading crates from the train on which Lucia was on to a waiting cart when the police arrived, seemingly for the same same entities as You and Them worked for. 
Residents of the dark planet
The mysterious shrouded figures who reside on the dark planet may have sent emissaries to Night Vale. In particular, the Night Vale Post Office, following its unannounced reopening in February of 2013, seems to have been restaffed by the shrouded dark ones. Cecil Palmer reports that all post office clerks are now "strange, cloth-wrapped figures who hum, tunelessly, and turn in place instead of doing any official postal business. In addition, the entire customer line and lobby area is full of more of these cloth-wrapped figures, all similarly turning and humming." Night Vale citizens who attempt to enter the post office are violently assaulted with visions of the dark planet, and are charged 2 cents extra for postage stamps.
- You saw the dark planet lit by no sun; the sight compelled You to flee Your old life.
- Cecil sees the dark planet lit by no sun as he is attempting to fight his way free of the condos.
- Cecil, as a teen, recorded himself saying that the radio station was "like a dark planet lit by no sun".
- They also saw the dark planet lit by no sun.
- Lusia Tereshchenko saw the dark planet just before, or perhaps just as, she died in 1843.
- Cecil sees the planet during the rift in reality when his younger self, who apparently came through the rift, notices him in the men's bathroom of the station.
- Huntokar saw the planet just before the world ended as a result of nuclear missiles being launched in 1983. She also says she sees it while telling her story and that it is so close she may be able to touch it.