To Azrael, all the members of the Dawn Breakers, from No.1 to No.5 were like his closest friends.
Back on Earth, after Kael's suicide, he had been left completely alone, no friends, no family—reduced to nothing more than a lab rat in the hands of those who experimented on him.
But later, he met Felix and the others of the Dawn Breakers, who were in the similar situation and together, they had finally succeeded in escaping that hellhole.
Even though by then he had already lost all of his emotions, even in that hollow state, he still cared deeply for each and every one of them.
To put it simply, while on Earth, they had become the anchor points Ashara once spoke of—pillars that kept him moving forward despite everything. To him, they were as important as Ashara, Silas, and Kael were to him now.
And seeing one of them imprisoned inside an experiment tube and by the very same man who had tormented him and others back on Earth ignited an uncontrollable fury within Azrael.