- A reference guide and manual in Russian for Heroes 3.

However, in my case, I noticed the following. If a hero spent the night in a swamp with a fly in slot 7 and a neutral creature in slot 1, there was no penalty in the morning. But if it was the other way around, or if the positions were swapped, there was a penalty (the number of moves was reduced). At the same time, another hero with 7 monster slots, all of different races, in the swamp, had the same number of moves regardless of the order, both before and after spending the night (it was minimal).

The "stranger" can only be a neutral unit (not belonging to any of the factions) - this is a standard trick. The neutral unit is placed to the left of all the "native" units for that terrain, and in this case, the terrain penalty does not apply to it. Any other arrangement, and the penalty is applied. Spending the night is not relevant here. You can simply conduct an experiment during the day - while moving, for example, across a swamp, swap the positions of the fly and the azure dragon - the remaining number of moves will change. This effect also works for AI heroes.