The temper of a Thunder Giant Dragon is even more volatile than that of a Black Dragon, like, they just can't say things that hurt others, using a Divine Artifact to beat someone up... it's too impetuous.
It seems that after the incident where the Golden Giant Dragon Austin was beaten up, Thunder Dragon Erinna started to take her rivals a bit more seriously, whether it was him, the Human Viscount, or the "Evil Dragon" mentioned by the Young Dragon, she was probably prepared to give it her all.
On the day Golden Giant Dragon Austin and Erinna were chatting via projection, the Dragon Whelp was present and heard their conversation.
During casual chats these days, Erinna would occasionally bring up the topic of Golden Giant Dragon Austin getting beaten up with the Dragon Whelp.
As a result, the Dragon Whelp knew crystal clear about the "grudges" between the Golden Giant Dragon Austin and the wild Pureblood Black Dragon.