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Outer Wilds Wiki

The Hourglass Twins are binary planets orbiting each other. Ember Twin is mostly desert rock divided into two halves by a wide equatorial canyon, and Ash Twin is almost entirely made of sand laid over a black, rocky core. Both planets orbit very closely to the Sun.

The twin planets' gravitational pull on each other changes from time to time, resulting in a natural phenomenon where sand is passed from one to the other over the course of about twenty minutes, creating the "hourglass" effect.

One minute into the game cycle, the Ember Twin will start to pull sand from the Ash Twin. Once the flow of sand stops, the current cycle will soon come to an end.


The Hourglass Twins are the closest celestial bodies to the Sun (excluding The Interloper at its periapsis and the Sun Station). As they are relatively small planets, gravity is low compared to Timber Hearth, but not as low as that of the Interloper.

Sand Transfer[]

Over time, starting one minute into the game, sand will transfer from the sand planet to the rock planet, filling the inner caves, canyons, and crevices (including the ruins) with sand. Like an hourglass, all of the sand is on the Ash Twin at first, but then steadily "falls into" to the Ember Twin over the course of 20 minutes. When the Sun goes supernova and the current cycle ends, all of the sand will have filled the Ember Twin's deep cave systems; only a rocky core and a few skeletal stone pillars will remain on the Ash Twin.

Ember Twin[]

Ember Twin is primarily made of red canyons and cliffs, with cacti and various rock formations on the surface. The planet possesses a large canyon encircling its equator running to its core, into which the sand falls from Ash Twin. The planet has an intricate cave system with multiple entries and sections, which lead to and feature various Nomai structures and artworks. As sand begins transferring to the planet, the interior caves and tunnels soon become inaccessible, preventing the player from entering the caves or trapping them inside.

Escape Pod 2[]

The second Nomai escape pod can be found near Ember Twin's south pole detailing the events of their arrival on Ember Twin. The escape pod is embedded into the crust of the planet and creates an opening into the large Crash Site Caves beneath the pod. Trails of Nomai writing recount their history and mark trails which eventually lead to the Sunless City. Following other Nomai writings lead to other landmarks in the cave system, including a small grove filled with trees and an opening to the Anglerfish Fossil.

Sunless City[]

The Sunless City is a large ruined Nomai settlement located deep within the cave systems of Ember Twin. By following written directions left behind by the Nomai in the Crash Site Caves, the player must navigate through a labyrinth of dark tunnels to reach the city. The city itself is built into a massive vertical cavern, and is divided into four different districts much like the Hanging City located on Brittle Hollow, connected by a network of stairways and gravity lifts: the Anglerfish Overlook District, the Stepping Stone District, the High Energy Lab Trailhead, and the Eye Shrine District.

The middle of the city contains a lit central hub area built into the cavern wall filled with trees, and a Nomai control panel that switches on lights for each individual district.

While originally considered safe from the rising sand by the Nomai, erosion has opened up holes for sand to fall into the city, causing it to flood from bottom to top like the rest of the planet, sealing off districts and pathways.

Anglerfish Overlook District[]

The second highest district, it leads to a small cavern, the eponymous Anglerfish Overlook, where the player can view and fire a Scout at the Anglerfish Fossil from an opening above it, but is unable to enter its chamber from the overlook. This district serves as the main entrance to The Sunless City from the trail under Escape Pod 2. Due to the falling sand, a return trip from this district is often impossible.

Near the passage to the Anglerfish Overlook is a small, two-leveled neighbourhood of derelict Nomai houses. The bottom level of the district is a maze-like ruin filled with cacti, while the top level is a more open cavern, dotted with numerous sandfalls that connect to the lower level. While most of the sandfalls fall directly onto batches of cacti, one of the sandfalls leads to a normally inaccessible building deep within the district. Inside is a Nomai scroll revealing that an easy method of reaching the Sun Station exists on Ash Twin, as opposed to the more difficult method of landing via shuttle.

Stepping Stone District[]

The second lowest district, containing ruined Nomai homes belonging to children, and a passage that leads to the Stepping Stone Cave, a large open chamber with minimal footing and small, stepping-stone-like platforms that must be jumped between, at the bottom which lies the High Energy Lab Trail. The cave eventually loops back to the ruined Nomai homes and the Sunless City.

Nomai writings in the homes reveal that Nomai children frequented this district often, using it to access the Anglerfish Fossil using a secret entrance within the Stepping Stone caves - a hidden crack on the ceiling that leads into the Fossil cavern. As hinted by the writings, the entrance is best visible when a light is placed with the Fossil's mouth, such as from a Scout.

Eye Shrine District[]

The highest district, and acts as a temple to the Eye of the Universe, similar to the identically named district in the Hanging City. This district contains information regarding the Nomai and their search for the Eye of the Universe. The ground floor of the district is filled with pockets of Ghost Matter, with care being required to traverse it safely.

A door connected to the Eye Shrine District lies at the top of The Sunless City, leading to a trail to the Gravity Cannon. The trail, while filled with pockets of Ghost Matter and cacti, leads to a hole in the surface near the Gravity Cannon, and can be used to quickly access the Sunless City from the Cannon.

High Energy Lab Trailhead[]

The lowest district, which acts as the beginning of the trail that leads to the High Energy Lab on the planet's surface equator, marked by a long energy cable, leading from the city and snaking through the caverns. The trail is winding and particularly dangerous, being among the first landmarks to be covered by sand as the loop progresses.

The first half of the trail itself lies at the bottom of the Stepping Stone Cave, but the second half of the trail is initially inaccessible, with a powerful sandfall leading to a large field of cacti covering the passageway floor. Attempts at jetpack traversal will only result in the sandfall pushing the player into the cacti, and the loop must progress until the sand covers the cacti to be safely walked across. However, due to this long wait, little time is left to walk the second half of the trail before being filled completely by sand by the time it becomes accessible.

The second half of the trail contains several dead ends and scattered cacti, with the energy cable itself often passing through walls. The trail eventually leads to a long gravity lift to the caverns near the surface of the planet, and the path leads through the inside of an equatorial canyon bridge to a lift into the High Energy Lab. The cable leads to a surface cave on the bridge itself, which is inaccessible due to Ghost Matter.

Anglerfish Fossil[]

A large cavern containing a giant fossil of an Anglerfish can be found within the cave system, dubbed the Fossil Fish Cave by Nomai children. The cavern possesses multiple openings through which the Fossil can be seen, but not entered, including the Anglerfish Overlook. However, a single entrance exists in the form of a hidden crack on the ceiling, found in the Stepping Stone Cave in the Sunless City, hinted by writings left by Nomai children. How the Anglerfish came to be on Ember Twin is unknown.

A gravity lift above the Fossil leads to a chamber above that contains Nomai research into the Fossil and Anglerfish as a whole, discussing their blindness. The chamber leads out to the surface near Escape Pod 2 via a Nomai door.

Gravity Cannon[]

A huge cylindrical Nomai structure found near the equator of Ember Twin that can be accessed from the surface, used to launch Nomai shuttles on the landing pad with gravitational propulsion, as well as recall them. A door leading into The Sunless City is nearby that can be opened from the outside, albeit blocked by cacti. However, a hidden hole in the surface lies in the rocks above the Cannon, connected to a trail that leads directly to the Sunless City's Eye Shrine District.

The Cannon's controls can be used to launch anything on the pad into space, as well as recall a linked Nomai shuttle back to the launch pad, originally landed on the Interloper. Recalling the shuttle frees it from its encasement in ice, allowing access to the inside to discover more about its destination and crew, who set out for the intruding comet.

High Energy Lab[]

An intact Nomai structure built into the Twin's equatorial canyon, researching high energy warp cores, marked by a massive solar panel energy tower. The main entrance can be found near the surface of the site, but the mechanism to open the door is sealed from the outside.

As indicated by Nomai writing outside, the second trail leading to the Lab must be found in the lowest district of the Sunless City, which must be quickly accessed to avoid it being cut off by rising sand. A nearby bridge crosses the equatorial canyon and leads to a cave directly connected to the Sunless City trail, with a long energy cable leading from the solar panel tower to the City itself, supplying power to the City. However, the cave is filled with Ghost Matter, and is thus nigh-impossible to cross alive.

The bridge, however, has a branch pathway that leads along the canyon to the Crash Site Caves, through a grove of trees.

Within the Lab itself, a large experimental testing area can be found connected to the solar energy tower, with two input slots for nearby spare black hole and white hole warp cores and a viewport large enough for a Scout to pass through. Attaching a black hole and white hole core to the slots causes a small black hole and white hole to be created in the testing area respectively - a complete warp core.

Controls for the solar energy tower are also present in the Lab, and power can be redirected from either the Sunless City (where it is by default) or the warp core testing area.

Writings and logs here reveal the Lab's history: after the Nomai discovered the negative time readings from the White Hole Station, Pye and Ramie were assigned to the High Energy Lab to attempt to recreate the phenomena. While Ramie believed that there was time warping going on, Pye remained convinced that it was a measuring error in their equipment that was causing the negative difference between arrival and departure times.

After rerouting power from the Sunless City to the Lab, they were able to recreate the experiment on a larger scale, proving that the holes were warping objects before they actually went through, much to the excitement of both scientists. This prompted the Nomai at the Southern Observatory to ask if the effect could be increased to form a 22-minute jump. These new demands necessitated the requirements of a more advanced warp core, increased space to house the device infrastructure, and an exponentially immense source of energy, all of which became the basis of the Ash Twin Project.

Henceforth, the lab became used to further development for the Ash Twin Project, and where the Ash Twin warp tower network was designed, based on the White Hole Station - with five murals drawn marking the six tower designs (with two connected towers for both Hourglass Twins). One such warp tower is linked to Ember Twin, with its warp receiver lying next to the Lab itself.

The negative time phenomenon witnessed by the Nomai can be replicated using the Lab's testing area - attaching the warp cores and firing a Scout into the resulting black hole in the testing area. The Scout will exit the white hole slightly before entering the black hole, resulting in a brief moment where two Scouts (causing a Signal Duplication error) exist at once. When power is redirected from the Sunless City to the experiment using the Lab's controls, this effect is greatly pronounced, as per the Nomai's findings.

A secret Ending and Achievement can be discovered by shooting a Scout at the black hole and allowing the Scout to exit the white hole, but removing the black hole warp core before the original Scout can actually enter the black hole, resulting in two Scouts and a temporal paradox. The second Scout causes spacetime to fracture, resulting in the game ending.

Chert's Camp[]

Chert's camp is situated on a tall pillar on Ember Twin's north pole, in the centre of a deep dry lakebed. Their camp is filled with astronomy equipment. As with other occupied camps, the player can refill their oxygen and jetpack fuel here. Over the course of the loop, Chert will slowly realise that the universe is dying, with stars reaching the end of their lives en masse, including the Sun, and become overwhelmed by this revelation.

Quantum Caves[]

The dry lakebed around Chert's camp hosts two Nomai entrances to caves opposite each other. Within, the Cave Shard can be found in a small chamber in either cave, with Nomai writings chronicling the mishaps of the Nomai researching it. Of note, the mysterious disappearance of their fellow, Coleus, in the Lakebed Cave, another possible location of the Cave Shard.

Quantum objects, including cacti are found in proximity to the Shard.

Lakebed Cave[]

A deep winding cave at the very bottom of the dry lakebed at the Twin's North Pole that very quickly fills with sand in the first minutes of the loop. The first level of the cave is a dark and confusing maze, with many paths blocked by stalactites. A sandfall can be reached that leads to a higher level of the cave, where eventually quantum objects begin appearing. Stalactites and fields of cacti frequently block the trail, but exhibit quantum properties, and disappear when unobserved and clearing their pathways.

At the end of the maze, a large chamber is present as the third possible location of the Cave Shard. A Nomai lantern with a switch to control it, as well as Nomai writings are nearby, revealing the chamber as the location of Coleus' disappearance, after the lantern unexpectedly went out.

Using the secret of the Cave Shard hinted at by the Nomai logs, the fourth location can be accessed randomly by standing atop the Cave Shard and briefly entering complete darkness (switching off the flashlight) to change locations with the Shard. The fourth location is a hidden underground chamber with no entrances or exits, containing musings from Coleus and his peers after his rediscovery.

Reading their writings explains the unexpected quirk of quantum entanglement, in which contacting a quantum object and ceasing observation, such as entering complete darkness, allows one to travel with the quantum object.

Quantum Moon Locator[]

On the South Pole of the Ember Twin lies the Quantum Moon Locator, a device built by the Nomai to locate and track the Quantum Moon. On the device itself are a set of concentric rings with five different symbols, each depicting a different celestial body in the solar system, each symbol points toward its respective planet. The fifth symbol shows the location of the Quantum Moon and which body it is currently orbiting, moving to align with the corresponding symbol. Nearby is a small Nomai ruin with information regarding the device.

It is noted by the Nomai and can be observed that the Moon disappears without a trace from the five markers, with the Locator being unable to find it. The Nomai correctly surmise from this that there must be a sixth location the Moon can travel to.

Texts and recordings[]

Ash Twin[]

Ash Twin is initially covered with sand, however as the loop progresses, the sand drains away, revealing a small rocky core and many artificial Nomai structures, most notably, the Ash Twin Towers, and the two large solar panel energy towers at the planet's poles connected to the Ash Twin Project.

Ash Twin Towers[]

A network of five towers built by the Nomai to act as teleporters to various locations throughout the solar system crucial to the Ash Twin Project, set on a massive ring around Ash Twin's equator. As the sand recedes, more of the towers are revealed.

Each tower visually represents the planet it connects to (for example, the Sun Station's tower looks like a sun, while Giant's Deep's tower resembles a cyclone) and contains a warp platform that can be used to warp immediately to and from the associated location when the corresponding astral body passes over the tower. The player can be teleported to the Sun Station, Brittle Hollow, Giant's Deep, Timber Hearth, Ember Twin and to the Ash Twin Project.

The towers were presumably designed by Phlox, based off of the White Hole Station with designs made at the High Energy Lab, and the six warp cores inside were created at the Black Hole Forge.

The Sun Station Tower, shaped like a sun, is the tallest, and thus the first to appear as the sand recedes. The path to the warp platform is blocked by large numbers of cacti, which must be traversed early in the loop using the sand to walk through the pathway before the cacti are revealed in order to reach the platform and thus the Station.

The Giant's Deep Tower, shaped like a cyclone, connects to the warp receiver on the Statue Island.

The Timber Hearth Tower, shaped like a Geyser Mountain, connects to the warp receiver near the Nomai Mines.

The Brittle Hollow Tower, shaped like a vertical section of the planet's crust, connects to the warp receiver on the Black Hole Forge District in the Hanging City.

The Tower representing the Hourglass Twins, made up of two towers with a bridge between them representing the Twins and the sand funnel, is notable for containing two warp platforms - one for Ember Twin and the other for Ash Twin itself. Both platforms are activated when Ember Twin (and its sand funnel) passes overhead, as the Twins share an astral body.

The Ember Twin Tower is larger and segmented in two, and connects to the warp receiver outside the High Energy Lab, with the Ash Twin Tower is smaller and connects directly to a warp receiver within the Ash Twin Project in the planet's core. However, the ceiling of the Ash Twin Tower is broken, allowing the sand funnel's pull to reach inside and potentially suck one out before the platform can activate. To reach the Ash Twin Project, a method of circumventing the sand funnel's pull must be used, either by using the adjoining bridge as cover or hiding in the closet on the opposite side of the room until the Ember Twin is directly overhead.

Ash Twin Project[]

The Ash Twin Project is a massive Nomai facility located within the excavated core of the Ash Twin itself. It is the source of the time loop that the player experiences throughout the game, and is considered the culmination of the game's secrets and discoveries. It is only accessible from the Ash Twin warp tower on Ash Twin's equator.

An enormous machine housed within a hollow shell of impenetrable ore mined from Timber Hearth, at the centre of which lies the casing housing the Advanced Warp Core, connected to the two surface solar energy towers on the planet's poles. A long pathway of Nomai structures is built along the inside of the shell, spinning at high speeds to create artificial gravity, with the Ash Twin warp receiver at one end. A projection pool surrounded by eight Nomai masks, three of which are active, as well as writings summarising the creation, progress and history of the Project, and controls for the Project itself lie along the pathway leading from the warp receiver.

The two switch controls at the end of the ring control the casing surrounding the Advanced Warp Core, and the ring's artificial gravity respectively. Removing the Advanced Warp Core will cause the Project to deactivate, and the time loop to thus end in that iteration if not returned.

With the Nomai Statues across the system pairing a sentient lifeform or computer (of which only three are active), the conscious memories or data of the paired entity are sent to and stored by the Nomai Masks within the Project. Powered by the energy of a supernova harnessed by the solar energy towers, the Advanced Warp Core would create a warp powerful enough to send the Masks' stored memories/data back in time by 22 minutes to their corresponding paired recipients. Thus, the 22 minute time loop is created, where memories/data of previous loops are retained.

The Nomai had intended to use the Project to discover the Eye of the Universe by brute force, by pairing a Nomai Statue with the Orbital Probe Cannon's Probe Tracking Module, and artificially inducing a supernova using the Sun Station. The Cannon would fire its Probe into deep space at a random trajectory, sending the probe's data to its Nomai Mask in the Project. Upon the Project's activation, all the stored data would be sent 22 minutes back in time to the Cannon, allowing it to select a new trajectory and fire again, adding more data to be sent back. The loops would continue until the probe found the Eye by pure chance, upon which the Project would shut down.

However, the station failed to induce a supernova, and the Project was put on halt until an alternative method could be found. This would not come to pass, however, as the Interloper arrived in the system, wiping out the Nomai with a catastrophic system-wide explosion of Ghost Matter. The Project itself would only come to accidentally activate many, many years later from the supernova caused by the natural end of the Sun's lifespan, as part of the heat death of the Universe.

Texts and recordings[]


  • The semimajor axis of the twins' barycenter is 5km. [1]
  • The twins orbit very close to the Sun, and thus it is not recommended to use the autopilot, as there is a large chance that it will try to fly through it.
  • Although the pillar of sand does not hurt the player directly, it can drag both the player and their ship up into Ember Twin from the Ash Twin, possibly resulting in a crash that will damage or kill the player.
  • If the player gets caught in the sand pillar whilst in their ship on the Ember Twin, they will be pinned to the ground unable to move for the duration they are covered. It is possible for the ship to become embedded into the sand during this and so unable to move at all.
  • For more information regarding the Hourglass Twins in the Alpha version of the game, see: Hourglass Twins (Alpha)


  1. provided by the Lore Explorer