This leads me to how to go about making a fantasy crop. I think one of the more important questions when developing a new crop for a civilization or race is:
What is the ratio between how labor intensive a crop's growth is, and how much food is produced? :
Some possible unique foodstuff examples and/or their attributes:
Eypharians have a small amount of fertile land to grow crops (Well, according to the most of the lore, a great river is mentioned somewhere, but I assume that idea was scrapped as I couldn't find it elsewhere). They also don't seem to be the kinds to take to farming much. I imagine they would be good at something like planting rice paddies, however. A high yield foodstuff might be appropriate for them, and due to their use of slave labor, it could be labor intensive. Not too labor intensive though, as they outnumber other races in their city. Something that perhaps takes well to extreme climates.
Maybe foodstuffs that produce allergies in all but one or two races. Or ones ones that are very picky about where, when or the way they are grown. Perhaps some that require more Djed absorption than others. Or ones that were specifically altered or created by the Valterrian.
Some other possible types of domesticated plants might be narcotic tubers, or other types of drugs. The effects of different addictive plants could be fun to explore. Drugs being outlawed could also produce interesting situations. They would have to be synthesized like poisons, though, if merely for balance issues.
Perhaps a crop that is unique to Sylira in some way, helping the city dominate or control the food market in their region, as they seem to.
I need some clarification on the way food works before truly diving into this, though. I read in the lore for Djed that it is replenished by food, does it take the place of energy in this setting? Are all the real world essential nutrients required for humans?
Any ideas, criticisms, insults and questions would be greatly appreciated.