NPC party members or helpers are a great way to increase playtime and lastability in an RPG. Not only are you gearing and levelling up your main character, you're doing the same for the NPC helpers. You are also increasing the player's engagement as they must learn about how the NPCs work, make choices about how to assemble their party, how to spec and gear the NPCs and experiment with different playstyles. In this section, I want to illustrate some systems that have been used in recently games to add NPCs into a single player experience.
Before we get into recent games, I'd like to reminisce for a moment about Final Fantasy VII. This wasn't, by a long shot, the first game to use a party system, but it sticks in my mind as one of the first times that such a system fully engaged me.
In FFVII, you chose to include three party members to your main group from a selection of many characters that were introduced slowly throughout the game. Two of the possible party members were, in fact, hidden (and optional), but finding them was fun in and of itself. Each character had their own special skills, but with the Materia system, you could equip the party with enough abilities to be able to accomplish all fights. Only members of the fighting party would gain XP during fights and only equipped materia would level up.
Naturally, at the time, I levelled all characters to the cap and all materia too, which took countless hours of fighting. But it was fun and rewarding. The need to see every character at a maximum level with their skills and abilities was the reason I spent all that time (in addition to performing the other side-quests in the game). I attribute this as the primary reason why this was the first game that I really sunk hours and hours of playtime into.
Lets move on a little and look at how some more recent games are handling NPC party members.
My first example is Battleheart. In this game, you don't have a main character, but a group of four that you can assemble from a pool of several different classes. Again, only characters participating in battle (and alive at the end) will gain XP. You must equip each character separately. As each character gains levels, they gain access to new skills. The fun is to try out different group compositions, try out all of the skills available to all of the classes and, of course, to equip all the characters in the best available gear. The play style of this game is very engaging - the only qualm I have is that it takes too little time to do everything in the game.
Moving on, my next example is another iOS game, Inotia 2 (and 3). In this game, you start off by choosing a main character. As you move through the storyline, you're introduced to the game's concept of Warrior Seals. Your first Warrior Seal is given to you as a quest reward. When used, a Warrior Seal generates an NPC "mercenary" based on the type of seal used. For instance, a Priest Warrior Seal generates a Priest mercenary. Each new mercenary will have randomly generated stats and a subset of usable talents. Pure luck determines how good the stats are and how many talents are unlocked. It is not uncommon to go through countless Warrior Seals to find mercenaries that either have inadequate stats or only a few talents available. The generated mercenary will start at the same level as your main character and will only gain XP while in your party. You can leave a certain number of mercenaries in the inn, but only mercenaries in your party will gain XP. Therefore, if you find a potentially good mercenary at a low level, but don't want to include that mercenary in your main party (due to group composition or the gamble that you may find a better one later), you will need to level them later on. Each mercenary can be equipped with the same number of gear slots as your main character. You can also switch control of the active member of your group at any time and manually control any party member. The mercenary classes are the same as those you can choose for your initial main character and your party can consist of a maximum of three characters.
The system used in the Inotia series is thoroughly engaging. Not only do you spend time having to learn each of the six classes, you need to make choices about your party composition, gearing (and there were a lot of gear choices) and which ones to level. At any given time, you might find a new Warrior Seal that yields a better mercenary than the one you already have, However, there are certain book drops you can use to improve talents on any character or unlock new locked talents, and some of these books are unique quest rewards. Therefore you have to choose whether to use those on a current mercenary or wait for a potentially better one. Luckily gear can be moved between characters. In my opinion, this party and NPC system goes beyond what we've seen in games like the Final Fantasy series and is probably the best way I've ever seen this done. The fact that you can switch to control any character in your party means that you get to experience the game-play styles of each class during one playthrough. However, only your main character can have all their talents available, so it gives incentive to play through the game with other classes.
The next game I'd like to look at is Torchlight. Torchlight gives every new player a pet (regardless of class chosen). The pet can be either a cat or a dog, but the difference is purely cosmetic. The pet functions as a pseudo tank (if needed), a dps boost, and can be equipped with spells and items. This allows, for instance, the pet to be turned into a healer. The pet has it's own bag space, the same size as your own, and you can send the pet off to town to vendor off all the items in their bag. This is really handy in a game where a lot of loot drops, but most of it is inferior to what you might already be using. Finally, the pet can be fed different fish (obtained from fishing) that temporarily transform it into a different beast. During this transformation, the pet gains the abilities of that beast in addition to any abilities you equipped on it already.
This is a very flexible helper system and one I have really enjoyed. The pet does not require any micromanagement and can function in a few different roles depending on your needs and the way you equip it. The pet does feel like a sidekick and, especially later in the game, is a lot less powerful than your actual character. I think of this pet as someting similar to what a warlock, hunter or death knight might have in World of Warcraft.
Moving onto the next example, I'm looking ahead a little into the future and at Diablo 3. Diablo 3 has recently introduced their new NPC system "Followers". From the Diablo Wiki (http://diablo.wikia.com/wiki/Followers):
"Followers are the new name of the hirelings that also appear in Diablo III. They have been revealed to have been improved much in the development process, including customizable skills and new appearances that change by leveling up and being equipped.
There are three followers available in Diablo III: the Templar, Scoundrel, and Enchantress. Each have their own reasons for fighting and a storyline that will progress in, but not detract from, the main story arc.
Only one follower can accompany you at a time, but even while not at your side, the other followers will stay with your current level so they can join you at any time without needing to be leveled up first in an easy area.
The followers are customizable enough to suit your style, depending on which four of their twelve skills you decide to develop. Each follower will be able to be equipped with two weapon slots, two ring slots, and also one of their own unique class-specific item.
You need to be in town to pick up your followers or switch between them, but you do not need to go back if they are defeated in battle. When followers are low on health, rather than die and require resurrection, they will depart from battle for an amount of time, then automatically return later. While gone, you will not receive any bonus from them."
According to sources, the three followers are a Templar that can be specced as either a tank or healer, a rogue that is a primarily ranged damage dealer with some crowd control abilities and an enchantress that is a primary caster or buffer class. Although there is nothing really groundbreaking about this system, it is nice to see that the NPCs have completely different skills to each other and also to any of the choices for main character.
I'm currently evaluating a game called "Companions" on the iPad. This game puts you in charge of independently controlling four party members. The dungeons are reminiscent of rogue-like games, with a graphical style similar to Gauntlet. The four party members are of fixed classes (one melee, one archer, one mage and one engineer), but each class can be specced in one of three ways. Each class has 3 skills, which differ depending on spec. Characters can be levelled and geared with drops. I haven't really had enough time with this game yet to evaluate everything that can be done, but so far it feels in some ways similar to Battleheart, but without the line-drawing mechanics.
Finally, a popular game that uses this idea is Dragon Age. There isn't anything really special to say about the gameplay mechanics of these NPCs that I haven't already mentioned about other games. They are part of your party, you choose a few to participate in fights with you, but those that are left out will gain levels with the others. They can be geared and specced in as detailed a manner as your own character can. The interesting thing about these NPCs is that you can interact with them back at camp and affect your main character's relationships with them by way of conversation or gifts. As is to be expected in such a high-quality game, the implementation of these NPCs is very detailed and each has their own storyline that can be explored. Much like in FFVII, you are introduced to the various available NPCs throughout the main storyline and the order in which you meet them is based upon your path through the game.
One thing that Dragon Age and Companions have in common is battle interaction. Battles can be paused in order to issue detailed commands to each party member, allowing fine-grained control of the situation which wouldn't be possible if the game were purely realtime. This is in contrast to Inotia 2 or Battleheart, where pausing combat does not allow you to issue commands.
Comparing all of the above games, I noticed that in games where the NPCs had less gearing and customization options compared to the main character, I tended to neglect gearing the characters, mostly just giving them "hand-me-down" items from my main. However, when playing games like Inotia 2 or Battleheart, I geared all of the characters with equal priority and care.
The amount of engagement and additional time spent playing a game which includes NPC party members is proportional to the options the player is given - gearing, speccing and also choices about how to construct the party. More options create more immersion since the player is compelled to spend time experimenting, whether it be with gear choices, party compositions or spec choices. Additionally, gear, gear enhancements, crafting materials and consumables must be collected for each party member to construct the optimum setup for attempting harder content, and this all takes time. Simple "default" NPCs such as those seen in Torchlight or for certain World of Warcraft classes do not noticeably increase player engagement.
One innovation in NPC party members that I think I've heard of is a more social-based system where you can bring avatars of your friends' characters into your group. This, however, removes part of the players own engagement as they slowly invest into each character in the party. Another idea that comes to mind would be a game who's available quests or story-lines would differ based on your party composition, thus creating the incentive for multiple play-throughs with different party compositions. Yet another idea would be to create dynamic synergies between party members based on the party composition. A game where each separate class had passive buffs to other party members as talents would encourage a lot more experimentation than simply classes that have talents and abilities that only affect themselves. These synergies could be set up such as to change the play-style in profoundly different ways.