Zack Fair and his fellow SOLDIER First Class, Sephiroth, enter the reactor in search of the rogues, Genesis Rhapsodos and Dr Hollander. They fight Sahagin-like monsters, but with a strange mutation: they have the face of their missing friend, Angeal Hewley.
Further investigation discovers both Angeal and Genesis were parts of Project G, an experiment performed by Hollander to make a modern Ancient. The experiment was a failure and Genesis had begun to slowly degrade, and could make copies of himself on humans.
Hollander and Genesis arrive, and while Sephiroth deals with his old friend, Zack chases after Hollander until they reach the bottom of the plate. When Zack has Hollander cornered, Angeal arrives and shows Zack he is a monster by sprouting a white wing, then attacks. Zack refuses to fight his old friend, but the ground beneath Zack breaks from Angeal's attack, and Zack falls into the slums below.
Following their successful attack on the Sector 1 Reactor, the members of the eco-terrorist organization Avalanche hope to repeat their victory on the No. 5 Reactor. After climbing through the city's underground subway system they break into the reactor. Avalanche fights its way down to the main generator and plant the explosives. On their way out, President Shinra greets the insurgents; Shinra had known of the attack beforehand, and prepared the reactor as a trap for Avalanche.
The robot Air Buster is sent in to defeat the terrorists, while President Shinra leaves, certain of victory. The party destroy the Air Buster and as it explodes, Cloud Strife is caught in the blast and falls into the slums below like Zack had done seven years earlier.
Although the reactor explodes, it is later seen in use powering the Sister Ray cannon, indicating Shinra repaired the damage, unlike Mako Reactor 1, which was utterly destroyed and never repaired. This is odd, given that Jessie said she would make her next bomb even more powerful than the one that destroyed the Sector 1 Reactor, but is supported by the visibly smaller explosion that results. Given that Shinra had enough foreknowledge to set an ambush, it's possible the explosion was mitigated by them in some way.
Mako Reactor 5 doubles as Midgar's (and thus, Shinra's) largest weapons development plant. Development of the new Airbuster is underway when Avalanche infiltrates the complex on their second bombing mission. Jessie reworks her explosives the night before the attack to minimize damage and casualties. However, Shinra detonates the reactor themselves after putting Avalanche live on TV as the culprits. Debris rain down on Sector 5 undercity, with the slums suffering—something which Shinra plays to their advantage through manipulation of the press and mass media.
Mako Reactor 5 has an identical layout to the Mako Reactor 1, with a different entrance. It is reached through the lower Sector 4 Plate, which leads directly to a chute that can be slid down to the floor of the utility access room.
In Final Fantasy VII, Mako Reactor 5 differs from Mako Reactor 1 in that it has a blue and green tint while using otherwise identical screens. In Final Fantasy VII Remake, the reactor interior appears much more blue, and though the layout is the same, a different route through the reactor is visited that goes through several armories.
Reached via elevator from the utility access, the entrance is a laboratory of rooms with a gate leading outside. The gate can only be operated by lever machinery, which will only work if those pulling the levers move them in sync with one another. After opening the gate, a passageway leads out into Sector 5.
In Final Fantasy VII Remake, the entrance laboratory also contains waste storage near the security lever, the door to which is opened by the same security mechanism.
The utility access is the first area the party visits after crawling in through the Sector 4 Lower Plate. It is an expansive room with brick walls and metallic pipes, one of which is located near the top-right of the room by a door leading in from the Lower Sector 4 Plate. This pipe can be slid down directly to the bottom floor of the room.
The room is built around a large central structure, with a staircase connecting the top of the structure. Atop the structure, a door to the elevator is located, along with a smaller round tower at the center that is climbed using ladders. At the room's floor is an armory, which in Final Fantasy VII Remake contains three storage ports for mechs, with the Airbuster located in the middle port. A door from the armory leads to the mako storage upper scaffolding.
Seen only in Final Fantasy VII Remake, the assembly plant comprise a series of laboratories on four different floors, linked to a hallway from the core at the bottom of mako storage. The rooms have terminals operating machinery used in the construction of the Airbuster, as well as other lab equipment. The facilities are separated by stairway ramps with turret defenses and construction sites seen in the rooms between the ramps.
The mako storage at the core of the reactor contains several metal pipes, fans regulating temperature on the walls, and large circular vents from the ceiling. Scaffolding and piping is descended to reach the core itself at the bottom.
The core at the bottom of mako storage is reached through a ladder, and is surrounded by mako around two platforms connected by a catwalk. The core is surrounded by heavy machinery. In Final Fantasy VII Remake, after this ladder is withdrawn, a door opens to the facilities and control room.
Final Fantasy VII
The reactor is reached from the Sector 4 Plate. The path to the core and from the core seems simple, as the group plant the remotely detonated bomb then leave through the way they entered. At the entrance, a minigame is required to leave, as the three must open the gate at a security terminal by synchronizing their movements at Tifa's command to disable the lock. After leaving, the group are confronted by the Air Buster.
Final Fantasy VII Remake
All quests in the reactor occur in Chapter 7, "A Trap Is Sprung," when a party of Cloud Strife, Barret Wallace, and Tifa Lockhart attack the reactor. After a short path to mako storage to plant the bomb, Shinra set up a trap for Avalanche, in which they will be fought by the Airbuster in a televised battle broadcast around Midgar. However, the group have a chance to weaken Airbuster before it is fully constructed by removing parts
Mako Reactor 5's layout is identical to Mako Reactor 1, and the characters reference this in dialogue. However, different areas of Mako Reactor 5 are explored entirely in the form of the assembly plant facilities, making it play out differently. Additionally, the lever minigame to operate the security room to leave plays out differently as Tifa is controlled instead of Cloud, and an optional quest, "Waste Recovery", is added in which the minigame is completed more times to obtain items and materia.
In Final Fantasy VII, throughout the reactor, the background music is "Mako Reactor" (魔晄炉, Makō Ro?). In Crisis Core -Final Fantasy VII- "The Skyscraper of Iron and Steel" plays, and later "Combat" when chasing Hollander.
The Midgar arena takes place outside Sector 5.
Cloud collects his reward at AVALANCHE headquarters and turns to leave, but his childhood friend Tifa convinces him to join their raid on Mako Reactor No. 5.Description
Mako Reactor No. 5 is unlocked by completing Mako Reactor No. 1 in the Final Fantasy VII realm. Completion of this dungeon unlocks Mist Cave in the Final Fantasy IV realm, Zanarkand in the Final Fantasy X realm, and Sastasha Seagrot in the Final Fantasy XIV realm.
Sector 5 Reactor appeared during the exploration event "Destroy the Reactor", which featured two versions. The Easy version featured the Guard Scorpion as the final boss, while the Hard version featured the Air Buster as the boss.
Behind the scenes
At the core of the reactor where the bomb is planted, the structure reads "1997", the release date of Final Fantasy VII, and the Greek, "σμκινσ", which roughly translates to "smkin", the name given to the rooms of the Sector 5 Reactor in the data. Interestingly, the Sector 1 Reactor reads "1998", and while there is text next to it it is indecipherable.