The difference of offline play in Heroes II and Heroes III.

Here, I remembered another thing:)
1) The difference in obtaining secondary skills.
In the second part, it is quite possible to obtain a new secondary skill, even if the hero does not have all secondary skills at the "Expert" level; in the third part, this is impossible.
2) A significant difference in artifact excavation. In the second part, when the "puzzle" is open and the landmarks are visible, you can see much more than in the third part. You can see mines, mills, and witch huts...; in the third part, the only landmark for excavation is the landscape, which, compared to the second part, makes the task much more difficult.
3) In the second part, there are a number of spells that can provide information about both the opponent and the "world" itself, i.e., show the locations of cities, mines, and artifacts...
In the third part, all these spells are combined into two, depending on two secondary skills - "Earth" and "Air".

A section on magic is definitely needed...

Definitely! ;)