It is said that in the three worlds, no existence is truly immortal in every sense of the word. And of course, that's true. No one is. For example, the Guardian Thrones of reality itself are not immortal; they can be killed, absolutely. But not just anyone can do it. There's a reason there are only three of them left in the heavens—there used to be five. One of them was killed by the sin of Greed, and the other… no one knows. At least, I don't.
On the other hand, the seraphim are the beings closest to true immortality. Beings created from the very essence of God, beings supposedly His children in the most personal sense of the word. No one knows for sure… and I don't either. But it is said that they, too, are not immortal. How to kill them? I don't know that either.
