The concept of Nirvana exists, sure. But it's a part of religious belief, and no one can prove that it's real any more than they can prove that Heaven or Hell are real.

[Apollo didn't think it could ever be proven, because some things were just beyond science. He already had proof that ghosts and spirit channeling were real, though he was generally a skeptic when it came to anything else in the realm of the supernatural or the extremely mysterious. ... This entire night aside, because Apollo was absolutely not ready to examine just what had happened to all of them yet.]

It's familiar in what way? Do you get mysteriously abducted a lot?