>>39439230>>39440593I sense I am summoned, so hello.
Regarding oases, they are basically outcrops of groundwater flows that extrude from the surface, usually in the form of underground rivers being elevated by the terrain. The water ultimately comes from the sky (as most non-ice freshwater sources are), so theoretically magic that can manipulate rainfall patterns could replenish the aquifers would be able to raise the water table and create/maintain oases across the land.
As for transforming deserts into vegetated land, you will want to have some ways to keep the land somewhat wet throughout the year, as that is necessary for grass to cover the surface and keep it from getting too hot (it is a positive feedback loop that likely led to the end of the Sahara green period). It is something that can be maintained through land keeping, but you will still need a certain amount of water in the system (and/or means to keep evaporation low) for grass to keep growing. In (eastern) fertile crescent, this is helped by the Tigris and the Euphrates which also helped introducing organic matter and silts from the Anatonian highland as sand is pretty bad at keeping water within itself.
I think /ehe~/ does have a similar enough hydrology that can be used for that purpose (see the coastal Levant for a RL example), especially if it is enhanced through supernatural means. Having arid biomes further away would also help the development of drought-resistant plants that can help the initial development of local civilisations.
