Reactor Raid, Sector 8 & 7, Second Reactor Raid - FF7 Walkthrough
When the game starts the very first thing you'll want to do is inspect the Shinra Soldier's body in front of you for two Potions. Follow the other members of AVALANCHE and go through all of the dialogue you're prompted with. This whole first part is rather linear so no real explanation is needed.
After Barret joins your party and Jessie and Biggs open the two doors for you, you'll want to go into the southern room and grab a Phoenix Down from the chest (pictured below). There's another Potion coming up too near Jessie - this one you can't miss since it almost blocks the route down.
When you reach the bottom floor of the Mako Reactor you'll find a Restore Materia as well as a Save Point. You can't use the Restore Materia yet so instead you'll want to use the Potions you got earlier to heal up your team before placing the bomb next to.... whatever that thing is.
This will begin your first boss fight against the Guard Scorpion. The Guard Scorpion is weak to Bolt, so use Bolt relentlessly on Cloud while you attack regularly on Barret. Heal with Potions when needed and you'll take the boss out in no time at all.
Note: For defeating the boss you'll win an Assault Gun, which is a weapon for Barret. Equip it before leaving this area to speed up the next few battles!
On your way back out of the reactor make sure you speak with Jessie and help free her leg. This is required to leave the reactor. Up top at the double doors talk to Jessie then to Biggs to get the doors open - then exit the same way we came in.
After you escape and go through a scene or two you'll find yourself in Sector 8 where you'll bump into Aeris (screenshot below). This encounter (as well as many others with Aeris, Tifa and Barret) have a ripple effect on later events. Specifically I am talking about the Gold Saucer date which happens later during Disc 1.
The only benefit besides different scenes is on the Ps4 Remake of FF7 you'll get the Best Bromance trophy if you go on the Gold Saucer date with Barret. If you'd like to learn more information about the Gold Saucer Date follow the link provided to go to that guide. If this is your first play through of Final Fantasy 7 I don't recommend you pay much attention to who goes on a date with you at the Gold Saucer.
In the room after meeting Aeris you'll find a Potion sitting out on the floor in the bottom left of the screen. After that room you'll be ambushed by Shinra Soldiers and you'll be given the option to fight them or run multiple times, it doesn't matter what you select but when you're done you'll find yourself on the train with the other members of AVALANCHE again.
On the train that's heading back to Sector 7 you'll want to speak with Jessie to advance the story forward (watch her demonstration on the computer) then speak with Barret. After you get off the train you'll want to follow the group back to the bar in Sector 7 known as Seventh Heaven. This is where you'll meet Tifa and Marlene. Give the flower to Tifa if you want a better chance of having her go on a date with you at the Gold Saucer.
To advance the story forward at the bar you'll want to do the following things...
1. Try to leave and Barret barges in
2. Go downstairs and approach Barret
3. Go upstairs and try to leave for a scene with Tifa
4. In the morning speak to Tifa then to Barret
When you're done inside Seventh Heaven exit and explore the town. I'd recommend buying another Restore Materia and a Fire Materia from the Materia Store as well as some Iron Bangles for your characters from the Armor Store.
The only treasures to find in this town are on the second floor of the Armor Shop. Immediately to the right after entering the area you'll see an All Materia sitting on the ground (pictured above) pick it up then the guy will lower a chest down from the ceiling with an Ether inside. Once you have both of these items you've gotten all you can collect here.
Leave through the northern part of town, the same part we entered from and go back to the train tracks. Go inside the train and speak with Tifa when asked to advance the story forward. If you get a moment speak with the man in this train car for a Phoenix Down, in the next car the black guy closest to the screen will give you a Hi-Potion if you speak with him and answer 'Yeah...'
In the next car someone will steal some of your Gil (you'll hear the Gil sound when you run by him) if you want your Gil back talk to him. It doesn't matter if you fail to make it to one of the next cars, it just means you'll be running through the tunnels in the screenshot below for longer.
At the southern most end of the tunnels when you hit the beam of lasers you'll find a vent off to the left side of the screen. Go down that and collect the Ether, in the big room go up the ladder Wedge is standing in front of and collect the Potion in front of Jessie.
In the next room after Jessie you'll find a Tent as well as a Save Point. Climb up the ladder than take the slide down into the reactor. The layout is the same as the last reactor we did, go down to where we placed the bomb last time to place another. Return to the top of the reactor but this time take the stairs (just like the previous one).
After you ride the elevator up you'll find a treasure chest with an Ether inside of it and a room with three buttons that you have to hit all at the same time behind it. Successfully hitting them all at the same time will open the shutter gates for you, allowing you to pass.
I'd recommend using this Save Point as there is a boss coming up that may be a challenge if you've ran from like every single battle thus far. It's another mechanical boss, so it's vulnerable to Bolt - Use that on Cloud every turn, Heal on Barret and just pound away at him.
When the battle is finished there will be a long story segment, after which Cloud will be split up from the group and wake up next to Aeris in the Sector 5 Slums.