The Finale is the final test chamber in Portal Stories: Mel. The boss battle against AEGIS takes place here. The level is focused in the use of turrets, but it also features electrified water or goo as a hazard.
After entering the main room where AEGIS is, go to the right room. Proceed to the turret dispenser on the back. Use portaling and jumping on furniture to avoid the electrified water, or use portals with the water flow to extinguish the fire and portal to the back.
A white turret will be in the dispenser. Use it to destroy AEGIS' servers. Should the turret die, another one will respawn in the dispenser.
After destroying all of AEGIS' servers in the right room, return to the central room. AEGIS will start draining oxygen, limiting you with 4 and 6 minutes in Advanced and Story mode respectively.
Enter the left room and use a turret from the dispenser on the far side of the room to destroy the servers on the bottom floor, like you just did in the previous room. Take care because a 50's turret will appear here, as well as on the second floor (those can harm you).
Go upstairs and grab the 50's turret near the window. It will explode, breaking glass and making it possible to open a portal upstairs. Use one to bring a friendly turret to destroy the servers here.
Use a portal under the now removed window and one near the ceiling to the right of the turret dispenser to fling yourself with friendly turret to the last server room and destroy the remaining servers.
Without the servers, AEGIS will stop attacking (the timer will stop) and can be entered for manual control. Fling yourself to its bridge and open the hatch that says "You must sign an NDA before looking at this".
A series of cutscenes starts. From here on, no user interaction is required.
Virgil remembers that there was another mechanical life form that AEGIS was trying to kill and tells Mel to discover who was it. The second mechanical target is revealed to be GlaDOS.
Virgil complains that he and Mel may have done something wrong but tells you to shut off AEGIS anyway. The process requires a password: 2056 (not required to type by player).
The Death Fizzler blocking the elevator is deactivated due to AEGIS' shutdown. Virgil tells Mel to put the Portal Device in the incinerator because the gun isn't allowed to get out of Aperture Science. Virgil says farewell to Mel, remembering everything they experienced in the escape. The elevator takes you to the surface, revealing a landscape with signs of human civilization destroyed.
The credits roll.
A fast camera flight through the underground facility follows, ending in the manual control room. AEGIS drains the facility’s reserve power, forcing Chell out of stasis, and Portal 2 begins.
The screen fades to black, with a receding chant of “nine" audible.
