I think that this depends on the species. And it's also a question of cultural perspective, as Atlanteans also don't eat horses or unsmoked fish.
The point from my perspective is Atlanteans don't eat horses due to their culture or taste but horses can be eaten. So a lore stating something technically wrong in an explizit way (i.e. Spiders cannot be eaten) somehow doesn't feel right to me.
How would it fit with spidercloth instead?
I prefer "spiders" because i think that its funnier.
From my perspective the fun comes from the clear reference to the Slogan of the 80's. I already imagined a fish breeder with a sticker of this Slogan attached to his back. For me thinking of eating Spiders isn't funny due to being not obscene.
And for the source I would suggest "prophecy of an old fish breeder", because prophecies are generally made by an individual.
This would be also okay. I searched a translation of the "Weissagung der Cree" and found only "Cree Indian prophecy", so I changed it to "Fish Breeder prohecy", to be as close as possible to the original.
According to Wikipedia this is a false cite anyhow.
After a second thought it fits better with the beginning of WorldSavior, but I am still somewhat unhappy with the spiders due to they are eatable. How would it fit with spidercloth instead?
maybe golden tabards.
But golden tabards cannot be produced if meat and fish are gone...
That why I choose spidercloth in my second attempt. As the atlanteans clearly love nice / valuable things and we should choose a ware that can be produced without fish or meat, what about the term " shiny tabards". This would be closer to the original anyhow.
I also think that pursued -> hunted would sound more natural in English.
the original is "poisoned", so I've chosen "pursued" because it looks similar.
What about "preyed"? And I might suggest to exchange Wisent with game as being a more general term for no meat.
So my latest Version would read:
"Only after the last deer has been shot down / Only after the last game has been preyed / Only after the last fish has been caught / Then will you find that shiny tabards cannot be eaten."