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This article is about the moon Alpha. You may be looking for the settlement within the shield or the episode.

We realized Sanctum was a moon, before we screwed everything.
Jordan Green [src]

Sanctum (mistakenly referred to as "Planet Alpha" to the Eligius III team) is a moon sharing atmospheric similarities to Earth. It is located in the Goldilocks zone of a binary star system, meaning it is in the habitable zone and has two suns. It is the closest world to Earth and probably the most like it. It was colonized by a team from Earth, and made up of four families, the Primes and another individual. Using Mind Drives, they continued their rule here for over two centuries. Like the other mission planets, it is within close proximity to a black hole.


The atmosphere is similar to Earth's, containing 77% nitrogen, 22% oxygen, 0.5% of argon, 0.2% of carbon dioxide, and small amounts of a new, unidentified element. Due to having two suns, it was believed that the moon's surface has higher radiation levels than pre-apocalypse Earth. To counteract that, the Eligius Corporation used the Nightblood serum on the members of Eligius III going to the moon. However, Nightblood was later discovered to be unnecessary for the survivors of the Battle for Eden, since the radiation levels are revealed to be good.


In 2045, Eligius III arrived to this moon. The Eligius Corporation was looking for a source to tap for oil, since Earth's oil reserves had run dry. The crew had undergone the blood alterations from Becca Franco's Nightblood serum, in case the radiation levels were too high. According to Eligius IV's records, if they ever reported back, it was after Apocalypse One, when no one could have received the call. The true results of their arrival remain unknown. Its later suggested by Gabriel Santiago that the choice of Sanctum as a destination was not a coincidence with the Temporal Anomaly on both it and Skyring, also known as Planet Beta.

Centuries later, Monty Green, after 30 years of research, cracked the code-locking on the Eligius III files while on Eligius IV, and set the mothership's coordinates to travel to the new planet (not yet identified as a moon). The ship's journey lasted 75 years. Upon arrival, Monty and Harper McIntyre’s son Jordan Green woke from cryosleep as his father intended. He went on to follow his father's instructions and woke Clarke Griffin and Bellamy Blake. He shows them his father's video files, explaining their life on the mothership, and the new world they could call home.

After the human race transcends, including Sanctum's population, the moon is left abandoned by all but its wildlife.

Celestial Events

Red Sun Eclipse

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The moon undergoes a celestial event in which the two suns eclipse, triggering the release of a psychosis-inducing toxin from the plants. During the eclipse, sonic anomalies are sometimes caused by molecular vibrations in the air and trees. When exposed to the toxin, all fauna are affected and goaded into violence. Those killed after the eclipse is over are consumed by the plants and trees. This celestial event and the toxin itself are known as the Red Sun. According to Gabriel Santiago, Josephine Lightbourne theorized that these events are why higher lifeforms never evolved on the moon.

In "Red Sun Rising", the eclipse is shown to have different effects on each person, targeting a strong personality trait or belief in each and every one. In Murphy, Emori, and Russell, the eclipse targeted their survival instinct in making them want to preserve their own lives by killing everyone around them. In Clarke and Echo, it targets their grief: Causing Echo to hear voices from her past as a spy to the point of sedating herself to make them stop and causing Clarke to hallucinate hearing Abby's voice on a radio trying to convince her to commit suicide. For Bellamy, it targets his inner paranoia: while under the toxin's effect he attacks Murphy and Clarke with the intent to kill, remarked at the times Clarke tried to kill him and repeatedly stating he's protecting everyone by eliminating all the deceivers ("Only I can keep us safe." and "I'm saving us from both of you!") With Miller and Jackson the toxins manipulate their love for each other by causing the two to hallucinate the insects burrowing inside of Miller and leading Jackson to nearly accidentally killing Miller in an attempt to get them out. Finally, when Russell uses the toxin on the people of Sanctum, it turns them violent against each other, separating each other by believers and non-believers.

In "What You Take With You," Gabriel uses red sun toxin to help Octavia remember her time in the anomaly. According to Gabriel, he and Russell Lightbourne once used the toxin in a similar manner to determine if any of the host's mind survived after the implantation of a Mind Drive. The answer was no, but in doing so, they unlocked parts of their own minds, things they'd hidden from themselves, answers about what their greater purpose was. In "Ashes to Ashes," Gabriel explains to Clarke and Bellamy that the toxin is everywhere: in every leaf on every tree, in the soil and the rocks. Over time, the Primes had found other ways to harness its power. Simone weaponized it as part of her Adjustment Protocol while Gabriel focused on developing an anti-toxin.

In "Blood Giant," Sanctum undergoes another Red Sun Eclipse despite it being nighttime. Gabriel explains to Sheidheda that the Red Sun paints the planet that they're orbiting which is enough to trigger the effects of the eclipse even at night. As the Sanctumites run for Ryker's Keep, Emori drops the shield and lets the bugs in as a weapon. The bugs kill Knight and two members of Wonkru before being driven off. Raven restores power to the shield and everyone takes cover until the worst of the eclipse ends. During the eclipse, Gabriel experiences hallucinations of Josephine Lightbourne.

Temporal Flare

Main article: Temporal Flare
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A temporal flare seems to be a green light source in the sky that shoots out other green flares that burn, destroy, or "petrify" anything they touch.

In "The Gospel of Josephine", Gabriel (posing as Xavier) notices a Temporal Flare nearby. He tosses Diyoza a rope and tells her and Octavia to get out and run. Diyoza gets out, but she realizes that Octavia has no time. She tells her she will return. Octavia submerges herself in the quicksand-like substance and survives the Temporal Flare with only damage to a hand that was left exposed. Diyoza manages to dig Octavia out and they run after Gabriel/Xavier.

Temporal Anomaly

Main article: Temporal Anomaly

The Anomaly as seen from space.

The Temporal Anomaly, often shorten to the Anomaly, is a wormhole to other worlds and the source of the temporal flares. The Anomaly has also sent messages to Diyoza, Octavia, and Gabriel Santiago himself.

In "The Old Man and the Anomaly", it is revealed that the radio signals get absorbed by the Anomaly and retranslates in The Verge, where it's possible to pick them up here in endless, repeating waves. It is also revealed that the Anomaly does the same as the Red Sun and that the Anomaly has similar effects on plants, only it's "constant and weirder". The Anomaly gets into people's minds, causing them to hear things and hallucinate, sometimes their darkest fear, their deepest desire, and both at once.

In "The Blood of Sanctum", it is revealed that the Anomaly is controlled by a mysterious, ancient artifact of an alien origin, known as the Anomaly Stone. In "From the Ashes," the Anomaly is closed by Bellamy's kidnappers from Bardo, the Disciples, presumably in an effort to prevent pursuit. In "The Garden," the Anomaly is revealed to lead to Skyring which was Planet Beta and then from there to Bardo.

In "Hesperides," the Anomaly takes the form of a much smaller portal beneath the Verge where the Anomaly Stone is located.

Starting in "The Stranger," due to the Stone being moved, the Anomaly forms in the Sanctum palace instead and closes between uses.

Alien Lifeforms

Native lifeforms are largely floral in nature. Nearly all existing faunal creatures were classified by Josephine Lightbourne in four evolutionary branches: Insect, rodent, reptile, and the less easy to identify, coined "Guaiwu" ("freaks" in Mandarin).


A bug

In "Sanctum", Jackson can be seen with a native bug contained in a jar. Soon after, a swarm of the bugs attacks and chases the exploration team through the radiation shield, into a settlement.

The bugs appear to be omnivores, shown to eat both meat and plants, as observed by Jackson. The bugs travel in swarms when hunting. They also appear to be strong, the bug Jackson had trapped repeatedly slamming into the glass without injury. The bugs avoid fire. 

The bugs have hook-like legs and round eyes, like that of a fly. They have a small tail and hidden antennae.

There are also other types of insects and bugs, too, as they were seen in drawings and books, including the Lan Hudie rhopalocera.[3] Josephine Lightbourne had studied many of those different types of insects and bugs. In "The Gospel of Josephine," Josephine, posing as Clarke Griffin, suggested the use of a bug on Marcus Kane that could act as an alternative to dialysis. Abigail Griffin believed it would work, but as Eric Jackson pointed out, they simply lacked the time they needed to do the whole procedure in.

The Children of Gabriel used the paralytic darts that was derived from a beetle that Josephine discovered.[4] It can be cured with an antidote.

Gabriel Santiago was seen eating a dead species of bug in the caves.[5]

In "Blood Giant," during a Red Sun Eclipse, Emori purposefully drops Sanctum's shield, resulting in Knight and two other men being partially devoured by the bugs. The swarm is then driven off with torches, showing that they are afraid of fire.

Snake (Kepa-She)

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In "The Children of Gabriel", a hideous snake appears called "Kepa-She" in Chinese. It can degrade the poison from a body, caused by being exposed to the seaweed during the eclipse. The Kepa-She can be used for medical purposes.


During Red suns, seaweed can move around ponds or lakes and crawl into someone like a tapeworm. It releases a toxin within the victim, practically killing them. The person can be revived by the Kepa-She snake like John Murphy was.

In "The Children of Gabriel", during the red sun, seaweed crawled into Murphy when Bellamy almost drowned him in the pond in the village. Cillian lets the Kepa-She bite Murphy, reviving him.

Trees and other plants

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During the red sun, trees and other types of growth become dangerous as they can release a toxin making people and bugs psychotic. If a victim dies near plants, the plants will "consume" the dead, even if there is no red sun. They can also eat fauna and bugs. The Offering Grove is a place where people give human sacrifices to trees.

In "The Gospel of Josephine," Abigail Griffin suggested using a type of Sanctum leaf as a surgical mesh on Marcus Kane believing that it, along with a type of Sanctum bug suggested by Josephine Lightbourne as an alternative to dialysis, could allow her to successfully operate on Kane's wounds from Michael Vinson. However, Eric Jackson stated that it wouldn't work as the procedure would take at least 15 hours while Kane had ten minutes at most once removed from his cryopod.

Tree Sap

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After a Temporal Flare, the sap in the remains of fossilized trees becomes "mutated". When applied to the skin, it causes a time dilation effect – wounds heal faster, but it causes accelerated aging (caused by exposure to a Temporal Flare) is slowed down. Gabriel Santiago called the bottled sap, "Time in a Bottle".  

Former Residents

Primes and Mission Team Alpha


Children of Gabriel


Eligius Prisoners




Sanctum (City-State)

Main article: Sanctum (city-state)

The settlement, also called Sanctum.

A city-state, also called Sanctum, is a ministate that is located within the radiation shield. It was built to be a sanctuary for human race. The radiation shield protects the Sanctumites from intruders and dangerous lifeforms.

Ryker's Keep

Ryker's Keep is inside the cave system under the city-state of Sanctum. It is used to hide during the Red Sun Eclipse, so no one would be exposed to the toxins.

Offering Grove

Offering Grove

The place in the woods near the settlement which serves as a cemetery for the dead Sanctum citizens. According to traditions, the bodies are offered to the trees, so their souls could be in a better place.

Research Outposts

At least fourteen outposts were built by the colonists or their descendants for research.

They also built numerous observation blinds to study the native species of the moon in their natural habitat.

The Verge

The Verge

The Verge is a location near the the Anomaly. It was once one of Sanctum's research outposts. It is was used by Gabriel Santiago as a home and study. The moon's Anomaly Stone is located in a hidden underground chamber beneath it.

Due to the Verge's proximity to the Anomaly, which sucks up all radio signals on the moon, radio signals can be picked up there in endless, repeating waves.

In "Hesperides," the Disciples take over the location and fortify it as their base before all but one is killed by Raven Reyes. Due to the Disciples' manipulation of the Anomaly, it now takes the form of a small portal in the underground chamber.

In "The Stranger," a force led by Knight extracts the Anomaly Stone and brings it to the palace.

C.O.G. Territory

The cave systems, where the Children of Gabriel live.

The Children of Gabriel Territory is home to a militant faction of rebels, known as the Children of Gabriel. They live in caves and other locations.

In "What You Take With You," one of the Children of Gabriel members named Jericho, began contacting a location called "Providence," in the C.O.G. Territory.


Season Five
Episode Appearance Status
Red QueenAbsent
Sleeping GiantsMentioned
Pandora's BoxAbsent
Shifting SandsAbsent
Exit WoundsAbsent
Acceptable LossesAbsent
How We Get to PeaceAbsent
Sic Semper TyrannisAbsent
The Warriors WillAbsent
The Dark YearAbsent
Damocles (Part 1)Absent
Damocles (Part 2)Appears
Season Six
Episode Appearance Status
Red Sun RisingAppears
The Children of GabrielAppears
The Face Behind the GlassAppears
The Gospel of JosephineAppears
Memento MoriAppears
The Old Man and the AnomalyAppears
What You Take With YouAppears
Ashes to AshesAppears
Adjustment ProtocolAppears
The Blood of SanctumAppears
Season Seven
Episode Appearance Status
From the AshesAppears
The GardenMentioned
False GodsAppears
Welcome to BardoAppears
The Queen's GambitAppears
The FlockAppears
A Little SacrificeAppears
The StrangerAppears
Blood GiantAppears
A Sort of HomecomingMentioned
The Dying of the LightMentioned
The Last WarAppears

Notes and Trivia

  • Before finding out that Alpha is a moon, it is erroneously referred to as "Planet Alpha".[6]
  • Jason Rothenberg stated that aliens will be introduced on this world.[7]
  • Season Six is set on this world.[7]
  • Rothenberg said that we would learn more about Eligius III and when it came to this world.[8]
  • This particular place in "Goldilocks Zone" refers to the world being far enough away from its sun to contain liquid, but still close enough to sustain life.
  • In "Damocles (Part 2)," Monty states that Eligius III came to this world to tap for oil as the Earth's supply was exhausted, even though the mission to Alpha and the other four worlds is described solely as a colony mission.
  • Sanctum is the Latin root of "Sanctuary".
  • According to Bellamy, Alpha is the closest of the five Eligius III worlds to Earth and probably the most like it which is why Monty chose Alpha out of the five.
  • Alpha is located twenty years journey away from Planet Beta on Eligius IV's damaged engines making Beta far closer to Alpha than Earth is.
  • Alpha is within close proximity to a black hole. Due to being closer than Beta, time runs slower on Alpha compared to Beta.


See Also