Umm, It's rain from the heavens since it mimics him. He fell from the heavens, and the heavens is just a term for space. Except Lavos is almost so God like, that it suits him, as if it is judgement day and he's doing the judging.
Anyway, it can't be a technological advancement or the hyper acceleration of objects OO.
At least it is like lil spikes that are under his shell and are released later, at most it is some type of Tech, and not necessarily magic.