The Rescue

65th Floor: Head upstairs to the 65th Floor. Collect "Midgar Parts" from chests to restore the model of Midgar in the central chamber. The chests open sequentially as you find the parts. The first part is in a west room, southern chest. The second is in the room south of that, southern chest. The third is north of the first. The fourth is in a green, glowing room north of the stairwell. The fifth and final part is in the room south-west of the model room, in the last remaining chest. Once all parts are collected, the chest in the stairwell will open, yielding “Keycard 66”.

66th Floor: Proceed to the 66th Floor. In the central rectangular room, go to the bathroom in the north-western corner. Enter a stall, climb on the toilet, and enter the air duct. Follow it towards the camera to spy on a meeting of Shinra executives discussing the "Promised Land". Hojo arrives and makes comments about Aeris.

67th Floor: After the meeting, exit the air duct and return to the stairwell. Hojo will walk upstairs, leaving the door open. You can follow him, but first, head back down to the 64th Floor to save your game. Return to the 67th Floor for some grinding. Steal a Hardedge from Soldier 3rds and Carbon Bangles from Moth Slashers. These are missable items. Once you have approximately five Carbon Bangles and at least one Hardedge, proceed west along the southern end of the floor, then north. Cloud will hide and encounter "Jenova". After the encounter, continue north through crates. Grab the chest near a Save Point to obtain the Poison Materia. Prepare for a boss fight: equip the chosen party member (Barret or Tifa) with Poison Materia + Elemental Materia in armor and Fire Materia + All Materia in their weapon. Equip Cloud with a Star Pendant. Ensure the chosen characters have Fire Materia + All, poison resistance, and Restore Materia. Save your game and take the elevator up.

68th Floor: Exit the elevator. Hojo releases his specimen into Aeris's enclosure. Barret shoots the barrier, rescuing Aeris and mauling Hojo. Another specimen escapes, joined by Red XIII. You must now fight them. Choose to send Barret away (improves his disposition) or Tifa away (lowers hers) to protect Aeris. The battle begins.