Partner characters, which may simply be referred to as partners or non-player characters (NPCs) are characters from throughout the Resident Evil series which serve to assist or simply just follow the main playable character. Up until and beyond the implementation of co-op in Resident Evil: The Umbrella Chronicles there are at least a few AI partners in each installment of the series. Although in many games these characters are later briefly playable or are playable through the player's choice. NPCs that the player never controls in any game of the series do appear here and there but are usually only able to speak to the player character and don't assist in any way.
Partners By Game
Both Rebecca Chambers and Billy Coen are playable characters for the majority of the game. However, the player can choose to switch between them at any time, and the one who is being AI controlled can be told to wait and follow. The AI character cannot switch weapons or use healing items but can reload if they run out of ammo. There are certain moments, such as the final battle, where Rebecca is strictly controlled by AI and the player has to use Billy to distract the Queen Leech.
In the original Resident Evil characters such as Rebecca and Barry Burton would not assist the player outside of cutscenes. This was changed for the remake. In REmake, there are a few different partners depending on whether you choose Chris Redfield or Jill Valentine.
As Jill, the player is initially assisted by Barry at the start of the game before he decides to explore the mansion on his own. If the player was able to give the Serum to Richard Aiken, he will help Jill fight Yawn in the attic. Richard mostly remains stationary throughout the battle but uses his Assault Shotgun to damage Yawn here and there. Regardless of the player's actions during the fight (whether they force the snake to flee or claim the Death Mask and run away) Richard will be killed. Barry later assists Jill during the fight with Lisa Trevor if the player allows him to keep his gun. He will actually run around and shoot but can be knocked of the edge and killed if Lisa manages to pull it off. Barry also follows Jill into the lab and is her partner during the final battle with the Tyrant.
In Chris' scenario, Richard does not aid in the battle with Yawn nor is Barry present to assist him in any situation. Instead, Chris' recurring partner is Rebecca and his partner during the Lisa Trevor battle is Albert Wesker. Wesker is not quite as active as Barry in the battle, he simply remains in one spot firing his Samurai Edge. This is problematic, as Wesker can be knocked of the edge and "killed" by Lisa during the battle if she gets too close to him; although due to Wesker's significance in the overall plot of the series, this instance is ignored, as the player meets him near the end, with no mention of his "death". Rebecca's role as Chris' partner is much different than Barry was to Jill. Instead of providiing ammo and items, Rebecca takes refuge in certain save rooms and can heal Chris. Rebecca is briefly playable if Chris is poisoned by Yawn. However, she cannot pick up any items in the mansion except the Serum and healing items nor can she use the item boxes or typewriters. A truly nonchalant player could explore a good portion of the mansion with these contsraints, but if Rebecca does not bring the serum to Chris in time and discovers his body, it is an instant game over. Rebecca takes Barry's place in the game's fnale; following Chris into the lab and assisting him the Tyrant battle.
In both scenarios, the character that the player didn't select becomes a brief partner following their release from imprisonment. But neither Chris nor Jill are able to aid in combat. Once they reach the roof, they are knocked unconscious by the Tyrant, leaving Rebecca or Barry to assist the player.
RE2 had a select partner that later becomes briefly playable depending on whether the player is controlling Leon S. Kennedy or Claire Redfield. If the player is Leon, it is Ada Wong and if its Claire, Sherry Birkin.
Ada follows Leon in certain parts of the game and can shoot enemies that get too close. Ada is briefly playable so that player can retrieve the Club Key and is also a selectable character in Extreme Battle.
Sherry follows Claire in more or less the same parts of the game where Ada follows Leon. Sherry cannot use weapons however, and is mostly resigned to hiding behind Claire whenever enemies are nearby. When Sherry is retrieving the Club Key, she seems defenseless but she has quite a lot of health, taking many hits from Cerberus before even going into Caution status. Zombies cannot directly attack Sherry however, and are forced to vomit acid on her instead.
Leon and Claire appear in each other scenarios from time to time. But they never assist each other in combat (even though this function was coded).
Early on in the game, Brad Vickers makes brief appearances fighting off zombies. When Jill meets him in a bar, he is busy engaging one. The player can choose to help him, but he will eventually kill it himself. Carlos Oliveira is also sighted in the streets fighting off enemies before Jill formally makes his acquaintance. In the restaurant and Raccoon Press building Carlos can help the player fight off Nemesis. Problematically, he can actually die druing these encounters, causing an instant game over. Carlos himself becomes playable when Jill is infected by Nemesis. He goes to the Raccoon Hospital to retrieve an anti-virus and engages many enemies along the way. Carlos is also playable in Mercenaries: Operation Mad Jackal.
None of the playable characters ever assist each other in gameplay. Steve Burnside is playable for a short period in the training facility and is also playable in Battle Game when he's not resigned to being a stationary NPC.
Leon is followed in most of the later parts of the game by Ashley Graham, who cannot defend herself but is able to hide from danger and can be told to wait or follow (much like in RE0). She later becomes playable after Leon frees her in the castle. Here is she still mostly helpless, but she can throw lanterns at Zealots that try to apprehend her.
Three different partners assist Leon in three different combat situations in the game. If Leon frees the dog caught in the bear trap at the beginning of the game, it will assist him in the first El Gigante battle. The dog cannot attack but mainly serves as a distraction. It is graceful enough to avoid most of El Gigante's attacks. The second partner is Luis Sera who assists Leon when they are trapped in a house surrounded by Ganados. Luis uses a Red 9 in battle and drops ammo and herbs for Leon if he feels it necessary. The player can choose to damage Luis or let the enemies attack him. Either way, if Luis takes too much damage, he will turn on Leon and kill him. The third partner is Mike, who aids the layer via helicopter when the player reaches the island. Mike will warn the player to get out of his way when he's about to open fire and can be fired upon, but not killed with friendly fire. during the last level in the game once the player deals enough damage to Osmund Saddler a cut-scene will show up showing Ada assisting Leon by giving him the Rocket Launcher, in a similar fashion to what she does in RE2's Scenario Leon B.
In Ada's Scenario "Separate Ways (The Another Order)" Ada can briefly see Leon in the first village level being chased by Ganados and the player can hear the chainsaw man chasing after him, although it was coded that the player would not be able to go after him or interact with him as Ada (because as Leon, the player never sees her). Leon later reappears in the Castle stage where Ada implies she "cannot be seen with him due to her having to kill him if she did" he can be seen attacking Zealots. He finally appears in the last stage fighting the mutated form of Osmund Saddler where the player as Ada have to make their way to the other side and assist Leon by giving him the Rocket Launcher.
As the first game to include co-op, Umbrella Chronicles technically featured partners at all time. Outside of co-op the partner cannot take damage or fire upon enemies, but do appear in quick-time events as well as cut-scenes. The various partners from Resident Evil Zero, 1, and 3 all appear in their respective scenarios (Rebecca, Billy, Jill, Chris, Carlos) but there are several redundancies throughout the game's exclusive scenarios (e.g. HUNK & HUNK, Wesker & Wesker, etc...)
However, in one particular case Richard Aiken assists Rebecca in both chapters of the "Nightmare" scenario. But the combined health meter of both characters says Rebecca & Richard. Richard has dialogue throughout the chapter and appears during the game's checkpoints, but he has no melee counter like the other characters and the game still considers the gunfire from both characters as Rebecca's attacks only.
RE5 was the second game in the series to implement cooperative play. But the player can still go solo, allowing Sheva Alomar to be an AI partner. Or the player can us "Sheva Mode" to make Chris the AI partner. In both cases the partners have to build up a certain level of "trust" before they will start listening to each other completely. The player can command a partner to wait, follow, attack, cover, assist with puzzles, and hand over equipment.
In either mode, Josh Stone is an AI controlled character who helps Sheva and Chris in various chapters. He later becomes playable in Desperate Escape alongside Jill Valentine. However, either of them can still be made into AI partners. The same applies to Chris or Jill in Lost in Nightmares.
Resident Evil: The Darkside Chronicles has a vastly different partner system from UC. Co-op or not, both characters present in scenarios have their own health meters and can take damage individually and fight independently. The only exception is the scenario "Darkness Falls" Outside of co-op the partner character physically appears on-screen while the main character is played from a first person perspective. Partners mostly attack with their default weapons, the handgun and knife, changing depending on how close enemies are. The partners from Resident Evil 2 and Code: Veronica all appear in their respective scenarios (Leon, Claire, Steve, and Chris) with Jack Krauser being Leon's partner in "Operation: Javier".
Three NPCs appear in the game however, assisting the characters or simply following them. Sherry and Ada reprise their roles from RE2. A new partner, Manuela Hidalgo follows Leon and Krauser in the new scenario. Similar to Ashley Graham She can be attacked by zombies in one chapter and later assists in the final battle with the V-Complex, utilizing the flammable blood she gains from her infection of the T-Veronica virus. She can cause minimal damage to the boss, and stun it to expose its weak spots.
In Resident Evil: Revelations story mode, partner is controlled by an AI only. They do not help you much in battle aside from scripted events. In some chapter, you have to venture alone or being apart with your partner while communicate via Radio.
Much like it's predecessor, this game also features CO-OP Play heavily, but beside the two characters that are assigned to players, the game also includes various NPCs, including civilians, BSAA soldiers, and police officers that can assist in combat with enemies or simply unlock doors and open passageways. Chris' campaign in particular has a team of at least four BSAA operatives following him and Piers for a few chapters. Leon's campaign features a few moment early on where civilians will take up arms and fight, but will usually die in scripted events. Jake and Ada's respective campaigns do not feature it a predominantly, but Chris, Piers, and their BSAA operatives will assist during story intersections.
The game features intersections/crossovers which can also be player online up to 4 players, an example of this is Leon & Helena's scenario crossing over with Jake & Sherry's scenario where they have to cooperate to take down Ustanak, Ada's scenario can also intersect with Leon/Helena and Chris/Piers and also Jake/Sherry where she saves Sherry later from an attack by the Ubistvo.
Resident Evil: Revelations 2 once again introduces the character switching "Partner Zapping" feature from Resident Evil Zero, the player can switch to the partner character at will. The most unique of partner character in the game is that the partner character take the support role rather than combat of the main player character hence their combat ability is limited:
- Moira Burton, Claire's partner character, can only use melee weapon and throwing projectile, her flashlight can stun enemies however.
- Natalia Korda, Barry's partner character, is limited in defense herself with bricks scattered in the environment, she also can sense the location of hostile.
- Evgeny Rebic, Moira's partner character in The struggle episode, can only use a sniper rifle and knife.
- Black Dress/Dark Natalia, is Natalia's partner character in Little Miss episode, she cannot pick up key items or open doors, and acts as Natalia navigator.