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

I looked at the heroes' skills and believe that a library is absolutely necessary for merging (half of the heroes initially have water and fire, while their main magic schools are earth and air). And it wouldn't hurt the Dark Gnomes either (they have a 10% chance to learn each school of magic).

I didn't take this into account; I will change the starting skills later. As for the gnomes, they probably inherited these chances of learning magic from the mages they replaced; I will look into it and revise.
I already created a table of spells with three additional spells (there aren't any in the first version).

All spells tied to one skill have a colored background, so you can suggest your own options on how to arrange the uncolored spells