Death came to the Bastion INviolate beneath a veil of shadow and flesh.
Castellan Lepidus outlived the command deck crew by a handful of seconds. They were asphyxiated as the machine-spirit lost control to the data-daemon and the airlocks and bulkhead doors were slammed open. The air shrieked out of the star fort, dragging many crew with it, kicking out blindly as they were thrown out into the void. Those who held on died in the next moment, blood vessels rupturing, lungs bursting, their blood coughed out into a frozen mist in the sudden cold.
A Space Marine could survive the void for a while. It was not the void that killed Lepidus. .