Born to a wealthy heritage, Iseult grew up knowing she was different. Her connection to animals was known in myth, but was a magic long absent from the people of the second kingdom except for her older sister. The golden haired princess understood the loneliness of being different; she was enchanted upon birth as well. They grew up only trusting each other.
After a devastating tragedy, Iseult's hair instantly turned from auburn to icy white. She isolated in her room for a year and upon emerging was noted as being quieter and exceedingly solemn. Unfortunately, Queen Eira and King Boreas were not young when they conceived their princesses and passed away shortly before Iseult's twenty-eighth name day. Only a few years younger than her sister, they agreed to rule together.
Although the original Targaryen families and those who chose to follow them beyond the Wall originally migrated as one, altering opinions and claims divided the people. To avoid unnecessary bloodshed each settled a lengthy distant apart. The accompanying ice dragon chose alignment with the first kingdom, called such since it was formed by the king and queen who first proposed travel beyond the Wall (to part from the continents' continuing wars and disputes).
With white walkers and wildings growing more bold, both kingdoms grew restless, worried the ice dragons aging would keep her from protecting them should full on attacks arise. Iseult -- with the whisperings on her sister in her ear -- rashly challenged the first kingdom for the dragon's allegiance, thus inciting turmoil between the former allies.