- "Sector Eridanus is a transcendent space with an inorganic control room and contrasting gardens. The hedge mazes that surround the control rooms put me in the mind of Alice in Wonderland. As for the central control room itself, it's a simple rectangular building. The walls are covered in monitors and control panels, as well as depictions of human history..."
- —Black box data, Shin Megami Tensei: Strange Journey 
Sector Eridanus is the fifth sector that the Red Sprite's crew investigates inside the Schwarzwelt.
Sector Eridanus, in stark contrast to the other Schwarzwelt Sectors before it, does not resemble any part of human vice or sin; rather, it's the Schwarzwelt's own idea of Earth after the eradication of the human race. Clean gardens, shining white walls and a considerable amount of rare technology all blend together around a huge tower. At the top of that tower there are multiple screens showing past images, moving pillars and a pure white expanse around a clear sky. In spite of Eridanus' beauty, it also contains the first instances of poison and sleep traps and has a huge area devoted to teleporter riddles and trap holes spanning two levels. In addition, later sections help establish that much of the beauty is actually illusory--the greenery is actually a hologram generated by the technology that is the sole true component of Eridanus.
The crew is initially elated to find that Eridanus, by all indications, is the last Sector, and that after they leave, the Schwarzwelt Joint Project will firebomb the entire dimension with nuclear bombs, presumably eradicating it.
The first mission posted by Arthur is to find the Vanishing Point, the Schwarzwelt's single exit point; he explains Eridanus is in a different point in space-time, and that if the crew kept following the trail marked by the Rosettas they would merely return to Sector Antlia. While exploring, the crew find an offline teleporter; when it is activated a demon is found guarding another teleporter, insisting his master had posted him there. Not too long after, the MC also finds a rare forma allowing Irving at the lab to improve his Forma Search function. Reaching Eridanus' top floor, the protagonist finds a secret locked door, behind which is the Vanishing Point. Unable to open it, he is forced to leave.
At Eridanus' top floor, the protagonist also notes his Demonica has data indicating he had been there before- which he thought was impossible. However, upon reaching that area, he finds the Norns and an inert Yggdrasil, who reveal they used to be the Disir he volunteered to help on Sector Bootes. With their powers replenished by Yggdrasil's pacification, they send the protagonist to defeat Yggdrasil in the past thorugh their timetravelling powers to save his past self from being killed at its hands. Once this is done, he returns to the initial point and leaves, again rewarded for his bravery.
Soon after this, Arthur notices disturbances that point to another ship in Sector Carina; the crew are ordered to pull out of Eridanus and investigate. Jimenez and the protagonist investigate and find a vehicle resembling the ones they used to enter the Schwarzwelt and hail it, believing it to be the Gigantic; however, Arthur realizes it is in fact the Lightning- the initial prototype of the Joint Project's vehicle, sold to a private organization. However, he also notes that the Lightning's systems, especially weaponry, have been heavily augmented.
Making contact, the crew of the Lightning introduce themselves as Jack's Squad, a mercenary unit sent to the Schwarzwelt in a search of treasure. Their leader, Captain Jack, proposes an impromptu non-aggression pact in exchange for three rare forma his team cannot locate and the superior Forma Search program. The protagonist agrees, and with Arthur's consent he returns to Eridanus to find the missing Forma.
Once the protagonist returns to Jack with the forma, the pact is sealed and they agree to part on neutral terms with the agreement to help each other in case of need. On his returns, the demon guarding the teleporter lets the MC pass and gives him access to Eridanus' full map. With Eridanus fully unlocked, the Protaginist finds his way to the upper levels and to Ouroboros, the Demon Mother of Eridanus. However, he's unable to unlock the doorway to Ouroboros and the Vanishing Point until he completes all of Jack's requests; once these are done, a Squad member gives him a superior Gate Search program, allowing him entry.
Upon reaching the Vanishing Point, the player meets Ouroboros, who is contemptuous of humanity, seeing it as bound to finite, sinful matter. She attacks, but proves to be undefeatable, as killing her only revives her in a stronger incarnation, and the protagonist is forced to retreat. During a conversation between Arthur and the protagonist, Jack interrupts to point out several dots funneling energy to Ouroboros. Once the demons at those points are killed, the "Torus of Infinity" is severed from Ouroboros, and she becomes vulnerable, although still more powerful than her previous iteration.
Defeated, Ouroboros releases a small energy band which the MC acquires. With the Vanishing Point open, the Red Sprite prepares to leave- however, The Three Wise Men interrupt their exit with a potent energy blast, damaging the Red Sprite and knocking them off course. The ship careen and loses control until its crash in Sector Fornax.
Sector Eridanus also houses the Four Heavenly Kings, as well as Aniel and Kazfiel fighting both solo and in tandem. Almost all of these fights have strict requirements that require special demons to overcome. The most powerful of all Fiends, Mother Harlot, is also present in Eridanus.
If after the initial battle on Sector Horologium the protagonist ends up with a Chaos Alignment, the final battle with Pillar Zelenin will be fought here.
Demons appearing in Sector Eridanus include:
- Bai Suzhen
- Gui Xian
- Tlaloc (Enemy Search)
- King Frost (Enemy Search)
- Red Rider (Enemy Search)
- Zouchouten (Boss; Ex-Mission)
- Koumokuten (Boss; Ex-Mission)
- Jikokuten (Boss; Ex-Mission)
- Bishamonten (Boss; Ex-Mission)
- Kazfiel (Boss; Ex-Mission)
- Aniel (Boss; Ex-Mission)
- Mother Harlot (Boss; Ex-Mission)
- Ouroboros (Sector Boss)
- Zelenin (Chaos Path Final Boss)
- Yggdrasil (Boss; Ex-Mission)
|Characters||Protagonist - Gore - Jimenez - Zelenin - Arthur - Bugaboo - Captain Jack (& Jack's Squad) - Ryan - Mastema - Louisa Ferre - The Three Wise Men - Mem Aleph - Kato - Williams - Muccino - Irving - Chen - Terry - MacCleary - Dent - Mia - Gekko - Anthony - Blair - Zoe - Maebe - Wolf - Tyler - Mackie - Mike - Dawson - Keema - Norris - McClane - Alex|
|Locations||Red Sprite - Sector Antlia - Sector Bootes - Sector Carina - Sector Delphinus - Sector Eridanus - Sector Fornax - Jack's Squad HQ - Sector Grus - Sector Horologium|
|Terminology||Schwarzwelt - Demonica - Demon Summoning Program - Delphinus Parasite - Magnetite - Macca - Moon Phase System - Cosmic Egg|
|Lists||Demons - Bosses - Skills - Forma - Equipment - Items - Apps - Extra Missions|
|Music||Shin Megami Tensei: Strange Journey Original Soundtrack|