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

Hmm. In my opinion, the level 5 mines are visually clear, and they are easily noticeable on the map, making it easy to identify their type. This cannot be said about level 7 and level 6 mines.

I don't think so. For example, it's hard to distinguish between a mine and a sulfur mine, and also a gold mine and a crystal mine.

Using sulfur and mercury in construction is complete nonsense, which is why I'm in favor of replacing all or some of the resources.

Well, if it's for decoration, then bone dragons require too much mercury. And devils require sulfur.

I didn't say it was for decoration. I'm talking about a service, i.e., maintaining these creatures in the city. Moreover, the concept of "a lot" is vague. If ore arrives, let's say, in tons, then rare resources are mined in much smaller quantities (for example, 1 gram of gems can be as valuable as 2 tons of ore).

Even so, dragons can use this to create an entire pool of mercury. And do devils feed on this gray substance? And do angels make necklaces out of gemstones?

Yes, such a huge amount of resources is unjustified, especially for such useless ones. Mercury, for example, is completely unclear why it's needed for creating dragons. Gems and crystals can be used in construction for decoration, but sulfur and mercury are only used by alchemists and mages.

My friends, let's not forget that training soldiers is a complex and time-consuming process. I used to wonder, "Why do dragons need mercury, and knights need crystals?" But compare the game to real life: we buy bread in a store for paper money and electronics for electronic money. The same applies to the world of Heroes. Crystals are used to pay for the work of builders, architects, construction material delivery personnel, major repairs, and hot water; they are exchanged for other types of resources (food, sand, and cement, for example). It is quite possible that the Academy of Magic uses guest workers from the Elven faction (or vice versa). Think bigger. Be glad that instead of all these complications, we simply give twenty crystals and get the building we need. Consider it the magic of the Heroes world.