Metal Gear Solid 5: The Phantom Pain from 2015 is the last entry in the storied franchise series creator Hideo Kojima worked on before leaving Konami. His exodus from the publisher was fraught with controversy, but the designer landed on his feet and came out with Death Stranding in 2019. Despite Metal Gear Solid 5 having a 5 in the title, it is not really directly connected to 2008's Metal Gear Solid 4.

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The Phantom Pain is more a direct sequel to Metal Gear Solid: Peace Walker, a 2010 PSP spin-off. With this in mind, there are several significant plot points in Phantom Pain and its prologue, Ground Zeroes, players simply won't understand if they did not play Peace Walker. If you do not have a PSP or Vita to play the 2010 game, you can also play it on PS3 as a part of the Metal Gear Solid: HD Collection.

8 Who Is Paz And Why Is She Important?

ground zeroes rescuing paz copy

Ground Zeroes involves Big Boss saving Paz and Chico. In the full game, the player also comes into contact with an imaginary version of Paz. If you did not play Peace Walker, you probably do not understand the complicated relationship she has with MSF and Diamond Dogs. She was an undercover agent for Major Zero and was sent to make Big Boss submit to Zero's plan or else be destroyed. Despite the revelation of her true nature, we still feel sorry for all the pain she goes through in Ground Zeroes

7 Dr. Strangelove

Strangelove Peace Walker

Dr. Strangelove is briefly mentioned in Phantom Pain and is relatively important to the end of Huey Emmerich's story. Huey kills her after she disagreed with the way he conducted his experiments. She is also Otacon's mother. She has a few bits of dialogue, but for a more comprehensive look at the character, it is recommended to play Peace Walker. In the PSP game, she is a major character and goes from antagonistic towards Big Boss to becoming an ally.

6 Who Are Chico And Amanda?

Amanda Peace Walker

The other person Big Boss saves in Ground Zeroes is Chico. He sadly dies after the bomb goes off in the helicopter. At least he shows up in the game at all. His sister Amanda is nowhere to be seen, only receiving a passing mention.

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They were both trusted allies in Metal Gear Solid: Peace Walker as local resistance fighters. They quickly joined MSF, the group that would eventually become Diamond Dogs in Phantom Pain. Chico was just a kid, so his death was particularly tragic.

5 Mother Base

Mother Base in MGS

This one is more connected to gameplay than the others. Anyone who only played the numbered entries was probably taken by surprise to find themselves recruiting soldiers and building up a base. All of these are expansions of elements introduced in Peace Walker and its predecessor, Portable Ops. In those games, players similarly manage where to put their resources and develop weapons and items. In Peace Walker the group is MSF, and in Phantom Pain it is Diamond Dogs. Phantom Pain takes the mechanic further by letting players walk around Mother Base and see the way it expands.

4 Huey's Revelations

Huey Metal Gear Solid 5

Big Boss rescues Huey from Skull Face in Phantom Pain. As the game goes on you realize that Huey is pure evil, having killed his wife and used his infant son as a test pilot for Metal Gear Sahelanthropus. While it is still surprising to see it happen in Phantom Pain, the impact is even more shocking for those who played Peace Walker. Strangelove's death is more tragic if you see the two meet for the first time and understand how shy Huey is.

3 Cypher

Screenshot Metal Gear Solid 3 Zero Para-Medic

Skull Face is out to destroy Cypher, who Metal Gear fans might better recognize as the Patriots. The group is only known as Cypher in Peace Walker, so you might be confused if you did not play it beforehand.

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At least Skull Face frequently mentions Zero, who is a major character in Metal Gear Solid 3: Snake Eater. It is not too confusing as long as you remember Zero and the conflict between him and Big Boss. It is a shame Zero only shows up in voice, however.

2 The AI Pod

AI Pod Phantom Pain

Despite the Boss having died in Metal Gear Solid 3, Lori Alan still recorded some lines for her role as the AI pod which recreates the Boss's personality. This plot point might seem kind of random, but the AI pods were an essential part of Peace Walker. Dr. Strangelove was trying to recreate the Boss's personality since she believed only the Boss could determine whether or not to launch a nuclear strike in the event of a nuclear crisis between the United States and the Soviet Union.

1 Kaz's Change In Personality

Metal Gear Solid 5 Kaz Miller

In Phantom Pain players find Kazuhira Miller after years in confinement, having suffered through torture. He is missing limbs and also has lost his sight. If you did not play Peace Walker, you might assume Kaz was always dour and focused on revenge. However, it was the events of Ground Zeroes and the destruction of MSF that changed him. In Peace Walker Miller is more joyful and a womanizer. He is even a bit of comedic relief in the portable game. We wonder if he gets some of his old self back in the years between Phantom Pain and his offscreen death in 1998's Metal Gear Solid.

Next: 10 Best Villains In The Metal Gear Solid Franchise