So, I’m thinking of ripping off Skyward Sword for a classic D&D setting. The lands are overrun by chaos. The remnants of law have retreated to a floating island in the sky. So, that gets me thinking about how big a community needs to be to be self-sufficient. What will be their source of water? How much land will they need to raise enough food?
Then I remembered how some people say how spells like Create Food would completely change a medieval economy. So, based on the 1981 Expert book, here’s the number of people (and their mounts) that a cleric can produce food for. (They can also supply water for at least this many.)
The spell will keep scaling up by 12 people per level, but the book’s spells/day listings only go up to 14th level.
That’s pretty impressive. The Wikipedia article on space colonization suggests that 50 people for the short term and 500 people for the long term are minimal populations to keep inbreeding under control. A couple of 14th level clerics could easily feed 500.
Which, so far, seems to essentially be the answer for Skyward Sword as well. It seems the goddess who created Skyloft provided a magic spring of water and supernatural agriculture.
This is also handy for isolated communities encountered in dungeons or the wilderness.
Looking over the rest of the cleric spells, it’s clear that—if a community’s clerics are generous—Continual Light, Cure Disease, Raise Dead, and the Cure Wounds spells are going to drastically improve the quality of life. Nothing too crazy, though. Interestingly, this version of the game doesn’t have any truth divining cleric spells.