It is entirely Biblical:
They are clouds without rain, blown along by the wind; autumn trees, without fruit and uprootedtwice dead. 13 They are wild waves of the sea, foaming up their shame; wandering stars, for whom blackest darkness has been reserved forever.
Jude 1:12-13
So even aftering dying the second death (the death of the soul) their is still their indestructible spirit which wanders in the Outer Darkness for eternity. How is this pagan?
Soul death is spoken of a number of times in both the OT and the NT, and yet not once is there ever a mention of spirit death. Spirit is indestructible according to the Bible. But from my experience it can become very brittle and shattered, the shards flighing off towards infinity in every direction. However, this is my own personal experience and there is no way to use that as an argument, there is no substitute for personal experience. All I can do is point to this one verse in the Bible that hints at astronomical wandering in darkness out beyond the quasars. And there is this verse which more than hints at the splintering of brittle dark spirits:
He will cut him to pieces and assign him a place with the hypocrites, where there will be weeping and gnashing of teeth.
Matthew 24:51
Note that there are 7 verse that speak of weeping and gnashing of teeth, two speak of a blazing furnace and three speak of the Outer Darkness (as paralleled by Jude 1:13).