From GamingWiki
Get a listing of major NPCs in the given campaign.
The only argument to this template is the campaign name, and if that is omitted the "campaign" property of the current page will be used.
Here is what this template looks like when called on a page belonging to the Ghost Town campaign:
{{NPC listing}}
{{#ask: is NPC in campaign::Ghost Town
|?high concept= | format = ul | template = SMW character list item | default =: No NPCs found for campaign: Ghost Town }}