Some changes for Hordes.
The modules are partially coded for multiplayer. Earlier stuff more than later. Things like cutscenes kinda work, with player 1 being the main one.
What's missing is several times the party as a whole is not teleported/transported to the next location, plus some other scripting that doesn't take into account other players.
Would be like other campaigns expanding the number of companions. It already supports 2 so most of the coding is there for more. Difficulty would dive off a cliff however.
This mod apparently fixes it, need to diff this: https://neverwintervault.org/rolovault/projects/nwn1/scripts/2072/
See subpage.