Entropy has a core, like Void and The Creator (the beeings whose fusion results in Entropy)
Their bodies are just vessels made out of hard light, it can get destroyed and rebuild as long as the core is intact. Although doing so repeatedly in a short span of time is rather taxing on the core.
The core is the very culmination if their beeing. It's... them, in their most reduced form. Since the cores don't exist in a physical state, they can't get damaged in the traditional manner. The core would be the equivalent of a soul or heart. To damage it means to inflict emotional damage, for example through trauma.
