Auzou Book for the dragon stones tome 2 the abyss of oblivion

In the war between the guardian dragons and the conquering dragons, Salomé is still not quite sure of her side. This doesn't stop her from stealing the Dragon Stone from Karl and his gang of Rascals, the most vile of dragons and a scourge of the school. From that moment on, Karl has only one thing on his mind: revenge. Even if it means reopening some corners of the Before-world that should have remained forgotten… and putting more than one dragon in danger… At the school or in the parallel universe of magical creatures, which dragon will come out on top?