Server crashed after player killed a magister from the Spellblades and such mod and then went near a portal from the mod.
crashlog says something about simply skills and spell engine
crash-2023-10-15_02.00.49-server (1).txt

can't restart server. it crashes again with the same thing

You are using outdates versions of the mod.
Please do not submit issues about outdated versions.

Update your installations, and feel free reopen if this occurs with latest versions.
It is strongly recommended to use the desktop applications of CurseForge or Modrinth, so you can actually see what needs updating, and can be done with a click.