“You're not supposed to be in here! You're going to ruin the surprise!”
The following section contains spoilers. Please finish The Second Dream before proceeding.
Gold rings circle and encapsulate the desolate moonscape – lavish architecture signifying the Orokin mastery over all things natural and technological during their reign. The opalescent halls stitching together what the enemy destroyed have been vacated since that era came to an end.
Lua is the Earth's moon, accessible as a location in the Star Chart. Once the seat of the Orokin Empire's power during their reign, it is now shattered and broken, scarred by the Old War. Formerly hidden away by the Lotus to protect the Tenno's secret, recent events have led to the reemergence of this lost celestial body, and now its fragmented remains are fought over by the Grineer and the Corpus, with Sentient fighters lurking about.
Lua can only be unlocked after a player completes The Second Dream. Both Grineer and Corpus contest possession of the moon since its reappearance, leading to Lua being the only other planet, besides Mars, that has (permanent) Crossfire missions. Sentients also appear in any of the missions, scanning for the player's presence and deploying fighters once detected.
Sentient units can be found and fought on this moon. Combat against them revolves around their ability to adapt themselves to the damage dealt by the player's weapons and abilities, requiring Tenno to have multiple types of damage (both physical and elemental) in their loadouts, or use Void damage to strip Sentients of their damage resistances.
Corrupted Wardens can be found in "Lua Rescue" missions.
If someone hasn't completed The Second Dream and tries to access any mission on Lua (via taxi or otherwise), they will be prompted to complete it before continuing and will be kicked from the party. Other party members who qualify will still be able to run the mission.
On most Earth missions during the night period, you can see Lua in the sky. The exception to this is, interestingly, the Plains of Eidolon and Cetus. Even if you have completed The Second Dream, Lua will never appear in the night sky; only its' remnants, identical to the ones found before completing The Second Dream, are there.
Besides the Halls of Ascension there are other puzzle rooms like the Lua Music Puzzle and the Arboriform room where the player encountered the Shadow Stalker during The Second Dream. The Lua Music Puzzle rewards the Octavia Chassis Blueprint and occasionally a Forma.
Before Update: Specters of the Rail, Lua was the name of a node on Earth, and the Orokin Moon missions introduced in Update 18.0 were considered Earth nodes. Specters of the Rail update subsequently moved the Orokin Moon missions to its own location, with the Lua node being renamed Cervantes as its previous name was then used for the new star chart location.
The name Lua for the Earth's Moon was foreshadowed by dialogue in The Second Dream, named as the place where the "rejects were consigned", likely referring to the Tenno.
Lua ties with the Orokin Derelict for the least amount of nodes of all the planets in the Origin System. While Lua's post-Orokin dimensions are unclear, the Moon is larger than Phobos, Ceres, Europa, Pluto, Sedna, and Eris.