Heroes 5.5 WarGame Edition - Tactical Edition.

I agree with Nargott that the most interesting of the discussed options is the ritual, but the question of whether this idea can be implemented still remains, which is why it makes sense to discuss other options, in case the ritual idea fails.
There is also another idea - in the city, in the guild of rangers, allow players to choose a larger number of sworn enemies, specifically, at the first level, one from each faction, at the second level, two from each faction, and so on, and in addition, remove the requirement to defeat the two-week growth.