There's an important thing that hasn't been addressed:
Skeleton illusion, certainly before this 2001 era update, is supposed to make you KOS to "good-aligned" NPC's, and by many accounts should make you non-KOS specifically against skeletons, at least lower level ones (
https://web.archive.org/web/20001118...ML/024974.html /
https://web.archive.org/web/20011125...ions.asp?Id=89 /
https://web.archive.org/web/20001206...ml?spellID=315).
Skeleton pets are also supposed to be KOS like that -
https://www.project1999.com/forums/s...01&postcount=5
It's the opposite on p99, where Amulet of Necropotence instead became this ridiculous item that allowed players to suddenly be non-KOS in all kinds of places and complete quests more easily. You're not supposed to be able to walk freely through Halas and Felwithe and such because you clicked AoN.
The change in 2001 about undead illusions not giving you amiable faction towards specific "evil" NPC's wasn't necessarily a total removal of its faction. They likely removed the beneficial impact of the illusion because it was too easy to get an OT hammer with it, but they still could have kept the downsides.