It would have been easy for Cain to hide Astrid's identity as an Atrox, but he chose not to. Inclusion and coexistence were critical if they wanted to blend their powers and grow stronger.
Although the Atrox race was supposed to be an enemy of the Godslayer Humankind, everyone here understood that there was no room for those feelings as there had to be a common goal in the fight against Dark Sky. That was why no one dared to show animosity toward Astrid, especially seeing how the Scarlet King guided her.
"Just focus your Ego Wave, a manifestation of your inner strength and will, on the book. After some trials, you will gain access to everything you need to advance," Cain explained as he focused on the book.