That said, the "one big nucleon" is pretty close in concept to a neutron star. It needs a few more nucleons than there are in a single atom though. Just a few. And it's not really a decay mode as it is a gravitational effect.
It's also kind of reminiscent of superatoms - clusters of atoms that act like one single atom - but that is very much not the same. (The nuclei aren't fused. They maintain regular, sensible, atomic distances. Electrons are free to pass between. etc.)
The skull presumably represents the finality of such a decay, given that the end stage of human decay leaves behind a skeleton, something that does not exist in nucleons. [citation needed]