The Queen of Witches, Baba Yaga (pronounced BAH-ba YAH-guh) invaded Golarion from another world in 3313 AR, making war on the Lands of the Linnorm Kings. Within 23 days the Winter War was over and she had established her realm of Irrisen. Once the Ulfen armies had been defeated, Baba Yaga installed her eldest daughter Jadwiga as queen of the new nation of Irrisen, and divided it into five provinces: Bleakmarch, Feyfrost, Hoarwood, Thronehold, and Wintercrux. After this was accomplished, however, the Witch Queen seemed to lose interest in Irrisen, and departed Golarion abruptly.
After founding Irrisen, Baba Yaga was not heard from for nearly a century. In 3412 AR, the Three Riders of Baba Yaga appeared in Irrisen. These strange, fey horsemen road about the countryside, punishing those who had been unfaithful to the Witch Queen, and (rarely) rewarding those who had stayed true to her, but offered little justification for any of their actions. The following year, Baba Yaga herself returned to Golarion and removed the Queen from the throne, placing her younger daughter Morgannan in charge. She left again shortly thereafter, taking along her eldest daughter Jadwiga along with the first generation of her descendants. This process was to reoccur every 100 years like clockwork, and continues to this day.
Not every daughter of Baba Yaga has quietly acquiesced to her mother's demand to give up the throne of Irrisen, and a few have even openly rebelled against the Witch Queen. Although the first three queens of Irrisen (Jadwiga, Morgannan, and Urvalane) are said to have abdicated with little fighting, Urvalane's successor, Pjallarane, did not go quietly. She and her children (the Jadwiga Pjallarane) launched an open rebellion against their progenitor in 3713 AR, but were ruthlessly put down by Baba Yaga in a single day in a conflict known as the 24-Hour War. A century later, Queen Aelena abdicated without the slightest hesitation, most-likely remembering her sister's futile struggle against their mother.
These relatively quiet successions continued through the reigns of Queens Harcatha, Sascha, and Karina, but came to an end with the Witchwar of 4213 AR. During this conflict, Queen Tashanna used the power of the Torc of Kostchtchie to summon the demon lord Kostchtchie and force him to assist her in fending off the Witch Queen. Despite this assistance, Tashanna and her followers were quickly defeated by Baba Yaga. Tashanna and the first generation of her offspring were dragged off to a place beyond Golarion, while her former loyalists were executed, and their bodies hidden in the necropolis known as the Veil of Frozen Tears.
After this unpleasantness, the next queen of Irrisen, Velikas renounced her throne quietly in 4413 AR, but trouble was once again stirred up by her successor, Queen Kseniya. When Baba Yaga came in 4413 AR, Kseniya attempted to take her life. Many of her children tried to do the same, but were ultimately prevented by the Witch Queen, who took them all with her and installed Betyrina as the new monarch of Irrisen.
Since Velikas' futile gesture of resistance, the Queens of Irrisen have once again given up their thrones quietly. It remains to be seen which of her sisters' footsteps the current Queen Elvanna will follow in when Baba Yaga returns this year