Silverwing I
Evan remembered Griselda's backstory in the game; where it was stated that the 'Unimaginably Powerful existence' that made her feel like nothing more than an ant waiting to be crushed before its might was what lit the fire of her desire for power.
In the game, when Griselda returned to the Alpha continent years later, she searched for Hydran, trying to see how the power she now possessed fared in comparison to him.
It wasn't explicitly stated that the being whom she met on the Alpha continent in her teenage years was Hydran, but the description she gave when she was searching for Hydran is what led players to figure out it was him.
She had stated she was looking for an 'Unimaginably powerful Existence' residing on the Alpha continent, and as for the description of this being;
It was something that had the head of a reptilian creature, with golden slit pupils and just the size of its head alone, was over a hundred metres.