Duel sets and duel generator.

This won't solve the problem 80% of the time. The issue is that you mentioned he has exactly 3 heroes. In my case, I've already added 21 heroes to the preset for the Knight faction, and 10-12 heroes for other factions. All of them exist in the map, but they aren't recognized by the game. So, simply adding a preset4 (and adding extra items in DuelPresets/map.xdb), or adding a 4th hero, doesn't solve the problem at all – the issue lies either in the executable file (which would be unfixable), or in some file with the number 3. The root cause of the limited selection is this number. Simply adding a 4th hero without changing this number 3 where it needs to be changed will 100% not solve the problem, because I've already done that, but the 4th to 21st heroes are just "in reserve." Since he has 3 heroes, it's most likely that this number hasn't been touched, and MOST LIKELY his heroes are simply set up and written in manually. In my case, these same heroes are generated automatically. If I'm wrong, that's good, but in any case, I don't know how to find these people and their mods.