I have no more details, unfortunately, because I wasn't the one who triggered the crash and can't reach the person who was. Here's the crash log, and here is the crash in the debug log.

Obtaining a similar crash, looks like its related to twilight mages who try to use the "Call of the Horn" spell. Here's my log too, if it helps
crash-2020-03-30_00.31.13-server.txt

Druid mages probably shouldn't be trying to cast it at all... guess I'll just disable that. Thanks for the reports.