Voc41
2
On a PvE Official server it’s possible to intentionally and or unintentionally kill thralls of other players.
If there is a 3 skull boss nearby, someone can train and or pull the 3 skull into your thralls.
The 2nd possibility is via the purge. If you’re neighbor summons a purge, the purge npcs can aggro your thralls on the way to your neighbors coffer.
Easiest fix for both of these is to put your thralls inside your walls. The other option is to talk to them. Maybe catch them in Global sometime or leave them a message with various in game signs/notes etc.