As soon as Adrian brought out the topic of the angels, the dragons that heard it suddenly flared up with great anger. Adrian expected that the dragons are furious, but their fury basically made the weather darken. The sheer anger made the surrounding mana turn dark and heavy which is related to a dragon's nature.
Unlike human mages, dragons can easily manipulate the elements around them or even just the mana around them. They are beings that are tyrannical when it comes to mana control. They do not control mana by assimilating it, but they subjugate it. The change in the weather is a manifestation of the subconscious control of the dragon.
"You ask that young demon which means that your kind must have been hit as well." The male ancient dragon stated in an angry but still polite tone to Adrian as he was not the subject of his anger.