It shouldn't have been a big surprise, considering his dragon was barely more than three months old. Winter's growth had been insanely quick compared to the usual Targaryen dragons, who could only be ridden after at least two or three years of growth. But his familiar was already bigger than the other two dragons after hatching. Winter also grew from the size of a large domestic cat to the size of a small pony in about two weeks during his stay at the Wall by feeding on its magic.