To a person with Claude's personality, his priority has always been the 'greater good'
If ten people have to die and suffer for the sake of a hundred lives, Claude would not hesitate to kill those ten
With the countless deaths present around him most of which were just normal civilians, his focus was entirely given to the Clay Doll Master
Seeing the faint flickering souls and Rezen literally crying tears of blood, Claude can already conclude what happened
Before he help people, he would investigate them first. If he learned that they were actually horrible bastards, Claude definitely wouldn't help them and even imprison or kill them if necessary
As such, Rezen's background including his parents is something that Claude knows and he recognizes the two faint souls
However... to revive the dead... even those that transcended the 6 mortal ranks would be helpless!
Claude casts Rezen a gaze of pity and he was about to apologize when...