Theoretically yes, so long as there were a fragment of the guardian and their light left, I believe that they can resurrect us from even a scrap of bone, however our power is limited by what light remains when we perish, if we are completely consumed like in areas with respawn restriction, it is safe to assume that our body, along with our light, are completely assimilated into the hive network of resources, knowledge or conciousness So much so that it's logical that our ghost cannot revive us and either flees or cannot survive the encounter itself Ghosts have one attack however, as seen in one clip, ghost I believe laser beams a knight or captain that is about to kill us, meaning ghosts aren't completely defenceless and Theoretically could fend off a wave of hive all on their own, stemming the darkness and potentially releasing the guardian from its new soul captor One would have to read further into the hives concept of sword logic and both the guardian and the ghosts understanding of it Its possible but not always, hell, the halo Easter egg at the top of the cosmodrome, that's that's guardian that's older than all of us apparently, though I believe lore wise, they gave him a different name