It seems the developer said that losing levels for a hero is a necessary measure. All maps in the Campaigns are self-contained; it wouldn't be interesting to play through the Campaigns if, after the first mission, the hero was already level 36. There is a narrative justification for why the hero loses levels and skills. When transitioning from the first to the second map, all spells remain, and the level and skills are not completely lost if you don't use the portal. A full transition of levels and skills will occur when moving from the fourth to the fifth map.

I haven't read everything the author wrote, but in this game, heroes are primarily about building a character. The work itself is simply amazing; I would say that if you add sound, this Campaign is no worse, and even better than the original, but I don't understand why the hero's level was reduced. The fact that he reached level 14 isn't a problem, but reducing all the main characteristics to zero is. Even if you don't visit any buildings that increase skills, the hero's characteristics at level 14 would be higher. After all, the whole point of the game is to defeat a large army with small forces due to the hero's skills and abilities. In that case, it should have been level 36, or even lower, anything but a full transition of the hero from one mission to the next, but each mission is more difficult, there are more enemies, and the hero's starting army is smaller. It would be good if the level and characteristics were reduced, but all the characteristics gained from visiting buildings and completing quests were retained.