If you were wondering: Ajax (fluffy cat) was born being a light element, meaning he has light aura... there are many kinds of magic in this universe, light being one of them, and every magical being is born with an aura representing a magical element. When Scarlet (bird) says she won’t kill him and she is “hardly so barbaric,” Ajax’s aura made the room lighter because he was calmer (it was dark because he was afraid). Now, when Scarlet said his daughter would do the honors, he didn’t believe her and he was still a bit calm. However, since his daughter was born being a darkness element, when she drew her weapon, the room went dark. This is why he knew she was behind him.