After I heard it a couple of times, I got what it was about, but it took me awhile to figure it was the Angel of Death doing the telling-which added more chill to the song...
The part that repeats “die by my hand, I creep across the land, killing first born men” has this chant underneath of “die die die...”
You barely notice it on the studio recording.
In concert the crowd does the chant. It’s quite noticeable and, without context, potentially terrifying.
Good fun.