Domain-level play is an old term for giving RPG characters political power in the form of ”domains” they control, be those guilds, corporations, or part or all of a sovereign nation. Historically, Dungeons and Dragons campaigns would eventually see the characters having enough wealth and influence to purchase a stronghold, which would give them not only a base of operations but also a parcel of land to see over. Once the characters were officially nobles in this way, a whole new area of storylines could open up, involving courtly intrigue as well as broader politics. At a default level this would insert characters onto a bigger political stage, but it was both possible and for some palatable to start changing the course of politics in the world in which the game took place.
In one word: politics.
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