Irene's research on wyrms for her presentation back when she was an apprentice was a bit lacking, to say the least. This was only because the most comprehensive research on the creatures had been done by the Sünstoian people and was not available in most libraries. After all, these beasts' natural habitat was in the cold north, where they could hibernate for long periods of time in the snow.
But Arthur knew. It was information he didn't expect to have to bring with him into adulthood because the last Sunsto who existed in this region were convinced they had slayed each and every beast.
Since they were unlike their dragon counterparts in warmer climates and didn't have wings, they needed a place to go where hiding was possible, and a place covered in snow was perfect for that.
