“[...] in a way that doesn't sound like it involves the slaughter of literally every living thing on Earth. [...]”
Isn't that what it's saying? xD”
It's a song about Beltane, which is a fertility festival...so, probably not. I interpret the cup as a reference to the metaphorical cauldron of life that things are *born* from, so it's not life-blood, but rather the blood and pain that come with all acts of creation. But, that is a bit difficult to render accurately.