Dying of old age with level 50 necromancer without amulet of life saving causes following message (second last line says my "-" glows in a silvery light):

You age... Suddenly you can see the Grim Reaper directly in front of you. She
speaks "Thou hast tarried too long. Now thy time hath come. I hereby
demand thy life!" Her scythe moves like lightning and runs through your body
as if through warm butter. Your life drains away... You die...
For a moment your - glows in a silvery light...
...in vain. Your time has come.