A mere seven
hundred souls, though they were Space Marines all, should
have made little account against such odds, yet Amhrad and
his Battle Brothers were determined that their sacrifice would
not be in vain. Bereft of hope, the Astral Knights fought
without fear, destroying every flux generator, weaponforge
and command node in their path. For one hundred hours
and more the Astral Knights wrought havoc. Yet each battle
amid the cyclopean structures that choked the World
Engine's surface took its toll in dead and wounded. Some
perished buying time so that their Brothers might fall back
and march to fresh battles. All died on their feet, spitting
defiance at the soulless warriors who opposed them.

Space Marine 5th Edition Codex pg. 44