A (Practical) Cast of Thousands
On the subject of group size, I would highly recommend not going above four regulars your first time out. Dungeon World is a game that demands a lot of the GM in play - you have to constantly keep in mind everyone's capabilities when you're pitching the setup to them and when they're pitching their actions to you. I've been running it for years now, off and on, and I can maybe take 5 people, or 6 on a very good day. You'll get a feeling for what you're capable of as you go, and a regular group can often entertain each other in ways that successive slots at a convention, say, just can't.
However, if you're anticipating a peripheral group who have some sort of interest in sitting down to play on occasion, I'd consider establishing a Crew, from the sadly-never-released Pirate World. The game was kickstarted and PDFs distributed to backers, but I can't find anywhere to buy it. (If anyone knows otherwise that'll be a nice surprise.) In a game of Pirate World, Crew are more than hirelings but less than PCs, who accompany the PCs regularly on their adventurers. In a game more based around a hub town or towns (and a notable Dungeon or Dungeons), Crew can be adapted to be the colorful townsfolk and friendly monsters and animal companions and such that you may be familiar with. They're statted out about like this:
Innismore, Irascible Alchemist
Hunger: Highly Illegal Ingredients
Benefits: Know something vital about a powerful adversary
Mix up a potion to overcome some obstacle
Loyalty: 2 Resilience: 1
The Benefits are the things they can do for you. When you want one of your Crew's Benefits, spend 1-Loyalty to get it, but first roll +Loyalty. On a 10+, that's the end of it. On a 7-9, the GM chooses 1; on a 6-, they choose 2.
- You must satisfy their Hunger before they'll help you again
- You must Defy Danger or otherwise put yourself at risk in order to make use of the Benefit
- It costs 2-Loyalty instead of 1.
Benefits are very conceptually similar to monster moves; that is to say, they don't have to be anything more than descriptions of the cool thing that you want the creature to do. When the PCs take advantage of them you'll usually have some kind of context to flesh them out (in this case, the obstacle or adversary PCs need to consult Innismore about). You can also define Benefits more strictly, as something to guarantee the PCs they wouldn't otherwise be able to find:
Whitecrush, Lizardfolk Shaman
Hunger: Forgotten knowledge of magic
Benefits: Provide access to a lizardfolk safehouse (a safe place to Make Camp for one night, and folk medicine to cure one debility)
Dispatch a young bravo as a guardian (treat as a hireling with Cost: glory in victory; split 7 points between Warrior, Protector, and Loyalty)
Loyalty: 1 Resilience: 2
The Hunger is the troublesome thing they need PCs to provide them with. When you satisfy your Crew's Hunger out of more than a sense of obligation, they gain 1-Loyalty. Hunger is something to keep in mind when you're offering PCs opportunities - sure you could destroy all the cultists' horrible reagents, but maybe you can smuggle them in to Innismore. Sure, Wizzrobe could copy their ritual notes into his own spellbook, but they'd also be worth bringing to Whitecrush. That sort of thing.
Loyalty is most easily altered through asking for Benefits and feeding Hunger, but it's there to represent how this person feels about the PCs. Doing things they would appreciate or putting them in danger can also bump it up or down, but it's proper sportsmanship to tell the PCs the requirements or consequences if they're making a decision and loyalty is on the line.
Resilience is a rough measure of how much damage they can take, equal to about 1 for every 5 full hit points they'd have as a monster. Each significant attack takes off 1 resilience, and if they get whacked at 0 resilience left their fate is completely in your hands.
Improving Crew is certainly possible over time, as PCs establish more of a relationship with them. If it seems like they'd gain something new, feel free to write some of your own moves that key off Loyalty to reflect these new capabilities - Whitecrush's bravos might get more points to distribute or she might develop some rituals of her own, or Innismore can kit the PCs out to "field test" some alchemist grenades (roll Loyalty and you get hold on low rolls that you can spend to activate complications).
When someone on the periphery wants to jump in for a session, they can pick up one of the Crew. They can use the main benefits as normal - they make the choices about costs instead of the GM - and they can also roll +Loyalty to help the main PCs in other ways, anything an Aid roll might work for. On a 10+ the PC they're helping gets a +2, on a 7-9 a +1, and on a 6- in addition to what the GM says, they feel obligated for letting everyone down and gain 1-Loyalty. In general they won't be exposing themselves directly to danger, but you've got Resilience for those cases where they get caught out.
