User blog comment:Miskos3/Fairy Tail 520: Dragon or Demon, Review/@comment-29874610-20170204151505/@comment-5303512-20170205012443

Well Deliora was under the temple, not actually in the temple itself.

And as for natural or Etherious demons, let's look at Devil Slayer Magic, it seems to have effected unnatural demons just fine, even regular demons are considered weaker than Etherious, I don't think there is any segregation between the types. So the underground cave would have no protection by the temple.