- "In sector Grus, all the sectors we've investigated so far are appearing as illusions. In some places, we can see traces of civilizations other than the ones we know on Earth..."
- —Black box data, Shin Megami Tensei: Strange Journey 
Sector Grus is the seventh sector that the Red Sprite's crew investigates inside the Schwarzwelt.
Upon arriving at Sector Grus, the crew sees that the outside images heavily resemble Sector Antlia; yet, the positioning system's coordinates do not match Antlia in the slightest; once the crew steps out, they find that the sector is, in fact, a random mishmash of the first four sectors: Sector Antlia, Sector Bootes, Sector Carina and Sector Delphinus. They also encounter a Dominion blocking a Sanctum device, claiming the crew needs permission from Mastema to access it. Curious, Zelenin agrees, and she and the Protagonist find Mastema further into Grus, who explains the sector's geography being a result of its demon ruler, Mother Maya, using her powers of illusion.
Zelenin makes several questions to him, and he always responds by gently but firmly rejecting the concept of human cooperation and ability to fight together. Zelenin leaves convinced Mastema might be saying the truth, but before they can progress any further, Arthur summons them back, warning about a hostile situation in Jack's Squad HQ. Ryan has revolted, killed the Red Sprite's overseers and begun organizing a rebellion with hidden weaponry and technology. Worried about this, thinking the crew have no options to fight back without bloodshed, Zelenin goes back to Mastema and requests he give her an easy solution out of the situation. Mastema responds angels of old could sing to "calm other beings and open their hearts to the Lord"-and Zelenin requests to be given such power, as his song carries no longer that power.
Mastema agrees to give her what she wants, and uses his power to transform Zelenin into an angel, making her reject her humanity and bow to his authority. Zelenin, now empowered, leaves with the crew to the squad's base. Once there, she uses a modified version of the angelic song to subdue the squad-but Jimenez remarks that the song has obliterated everything human in their victims, leaving them empty shells interested in serving the angels and nothing else. Disgusted by the brainwashing and the heavily detrimental effects of the song upon demons, Jimenez collects the demons being used in the experiments, excuses himself and leaves to Grus to live with what he sees is his new family.
Returning to Grus, the crew meets with the remnants of the experiments of the squad, and their leader, Grendel, who offers to unlock the path to Grus' underbelly if the crew kills the remains of the squad. Leaving to consider the choice, the Protagonist encounters a delusional Zelenin at the gates of Grus and helps snap her out of the illusion consuming her. Upon learning of the demons' bargain, she offers instead to blast the way open with her song. An alignment-affecting choice is foisted upon the player at this point: either kill Jack's Squad, their victimized demons, or simply kill the Grendel that is keeping the path sealed. If either Jack's Squad or the demons are killed, Zelenin or Jimenez will heavily censure the protagonist, either for killing servants of the Lord, or innocent, beleaguered demons. In either case, too, the door to Grus proper is opened and the investigation there can begin.
But before the Protagonist can go too far, the spectre of Commander Gore again appears, this time clad in his Demonica, stating the entire mission has been a total fiasco and nothing remains except die without dignity like the losers they always were. Rejecting this illusion, both he and Gore fight it until the older man, lost and confused, leaves to explore further and understand his powers better.
At the end of Grus' illusions, the protagonist finds Maya, who attempts to drown him into further illusions to make him fall. She fails, and dies, leaving behind her Exotic Matter and her rare forma. The crew, shattered by the conversion of Zelenin and the Jack's Squad situation, makes way for the final stretch of the journey - Sector Horologium.
In a section of Grus' Sanctum A, a Power guards a single door, stating he heard the voice of God commanding to guard him until dismissed. On a New Game, no matter which alignment, after the Jack's Squad mission, a Strike Team member will be there and offer the protagonist news of a rumor according to which a powerful demon guards a rare forma at the end of the tunnel. Should the protagonist agree to investigate, the second half of Grus becomes open, leading to a brutal deathmatch with Alilat at the end of the tunnels. Once Alilat's defeated, the Strike Team member will reveal himself to be a powerful angel who seeks pieces of the scattered power of God. He will also report that a much larger and powerful demon also lurks in the very depths of Grus, holding the remaining pieces of the divine power.
Should acquire the final Enemy Search program from rare forma pieces in Horologium, he will be able to reach Grus' B4F and reach the final sanctum, rejecting a female voice that begs him turn back, that of the Father of the Schwarzwelt - Demiurge. Far harder than Mem Aleph, the monstruous deity claims to be indestructible, unparalleled and perfect. Once the monstruous entity falls, the hardest mission of the game is over and the Demiurge rises, restored to its full power and glory, vowing to protect humanity... as long as they believe in the Holy Spirit...
If the protagonist chooses to follow the Chaos Alignment, one can talk to Grendel again, who excuses himself for doubting the Protagonist's prowess and refers him to a powerful goddess who has come to take Lady Maya's place - the demon goddess Mara. Upon meeting her, she will ask the Protagonist to undergo a task for her - to venture into Sector Horologium and disrupt the holy ritual several angels are carrying out to summon a massively powerful demon of Law - Seraph. If Grendel has been slain earlier, one can go talk to Mara directly after locking the Chaos Path; she will forgive the Protagonist and issue the mission anyway.
In Law alignment, Mara will be the target of Seraph's revenge instead. An Archangel will point out the site of the ritual to the Protagonist to allow him to make contact with the holy being, who will issue the mission calling for Mara's death. Once she has been killed, Seraph will descend upon Sector Grus, reward the Protagonist and offer to join him.
Demons appearing in Sector Grus include:
- Wild Hunt
- Garuda (Enemy Search)
- Heimdall (Enemy Search)
- Pale Rider (Enemy Search)
- Maya (Sector Boss)
- Mara (Boss; Law Path only)
|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 - Wailing Womb|
|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|