The giant skull that Malachi created in the sky seemed to be fueled by his own inner turmoil and negativity, and functioned somewhat similarly to a black hole.
The construct opened it's bony jaw and inhaled continuously.
A large suction force was created that inhaled all of the nearby debris, be it organic or inorganic.
Once anything entered the mouth of the skull, it was thoroughly ripped apart to only the finest of pieces and obliterated.
The longer the skull kept its mouth open, the more it started to pull into its destructive maw.
Even the impenetrable building where the blessed were being imprisoned was starting to be ripped apart, with larger and larger fragments coming off by the second.
Malachi tried to tell it to stop, but for whatever reason his mind was too cloudy to be able to properly control his new and terrible power.