RTF is a global modification that replaces all towns in the game.

I find it difficult to come up with ideas for Ashan; my brain doesn't work well in that direction.

The suggestion doesn't necessarily have to be grand; it could be something small that enriches the lore – for example: dwarves value pearls more than cave minerals / elves transform a magical wasteland into a forest using sacred seeds of Britigi / 6 elemental schools of magic are suitable for priests, while battle mages use the most optimal magic system from 4 schools divided according to the principle of impact.

Added 20 hours 38 minutes ago
I suddenly realized a simple thing – the main advantage of the new world is that at the beginning, you can use the standard Heroes of Might and Magic factions, rewriting the details to fit the new lore (and then do a retcon if necessary). In principle, the elf, demon, and undead factions in Heroes of Might and Magic V are very stereotypical and will fit into any lore, and some units can even be left unchanged.