Immunity: death magic not working?

[SalemBlackwood]

I was running around in the Underdark and the Duergar Priestesses were able to cast a Fort save V. insta death spell and kill me instantly - but I have a greater belt of guiding light on that grants Immunity to death magic and fear - I ran all around the underdark the last few days without a single death from them, but today (1/18/22) I got killed outright twice in a row within 5 minutes or so. Is this a bug?

[Garrett]

You were struck by implosion spell. While this spell is not death magic (immunity does not apply), the saves are made "versus death".

[SalemBlackwood]

Thanks! I must have just gotten really lucky last night. I ran straight through 16-18 of them and I guess I only have a 55% chance to pass the save lol.

[Stabbath]

Ah, been wondering about this. I've died three times with death. Wiz at marvale steps, druid leader in grove, and lich dude that drops essence for quest.