Hollow's Lantern

 is a relatively small but highly volcanic moon orbiting Brittle Hollow. The four volcanoes throw out balls of lava into space at random short intervals, slowly depleting the moon's lava reserves and revealing the moon's surface over the course of the loop.

Most of the lava balls fall on Brittle Hollow, causing parts of the crust to collapse into the black hole at its center. The moon has a very unusual axis of rotation, making the lava ball trajectory highly chaotic.

Volcanic Testing Site
One of the volcanoes can be entered after enough lava has fallen on Brittle Hollow. The inside of this volcano contains a Nomai ruin and text that can be translated.

It is revealed that the Nomai used the volcanoes on Hollow's Lantern to test ores from the Timber Hearth mines for their heat resistance, to see if the ore could be used to seal off the Ash Twin Project and protect it from the heat of a supernova.

Texts and recordings
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Volcanic Testing Site

 * Nomai ore testing
 * Nomai ore testing

ROOT: Friends in the Timber Hearth Mines, the last type of ore you sent us survives the longest in direct heat.


 * ROOT: Can you send us more of the same for additional testing? We’re attempting to improve its durability, and our forge has already burned through everything you sent!


 * OENO: We’ll deliver more ore to Hollow’s Lantern immediately. You must be fired up about crafting the Ash Twin Project ’s protective shell!


 * ROOT: Yes, the idea of an encasement that’s supernova-proof, however briefly, has kindled my curiosity!


 * ROOT: My gratitude! I imagine we’ll also have an updated estimate soon of how much ore is needed to seal off the Ash Twin Project.


 * OENO: Will it be more than we initially thought?


 * ROOT: It will be significantly more. The smallest crack or opening in the protective shell would destroy everything.


 * }

Trivia

 * Sometimes, a fireball misses the crust and enters the black hole of Brittle Hollow, causing fireballs to be found elsewhere in the solar system. Due to this, balls of lava can be found crash-landed on bodies far from Hollow's Lantern.
 * The achievement "Mica's Wrath" can be unlocked by destroying the model rocket by flying it into either the Sun or Hollow's Lantern.
 * Once the lava has emptied enough, a Nomai skeleton can be found in a lava-lake, giving a 'rock on' gesture with both hands. This skeleton appears to have a tail, which is not seen on any other Nomai corpses in the solar system.
 * The lava balls explode on contact with anything but the Scout, which makes it possible to prevent the destruction of Brittle Hollow.