Queen Siv and her trusted servant, Myrrthe, arrived at the Glauxian Sisters disguised as gadfeathers after fleeing from the Hrathg'har ridge and the invasion force led by Lord Arrin that had resulted in the death of her mate, King H'rath.
After having been there for not too long, Myrrthe determined that the sisters of Glaux, including Rorkna, were under the influence of nachtmagen, more specifically, the Nacht'ga. They immediately left upon discovering this knowledge and headed to the Ice Cliff Palace.
In Beyond the Beyond, Grank recovered from his stupor caused by the Ember of Hoole and flew immediately to Elsemere Island after hearing news of the deadly invasion on the Hrathg'har ridge by Lord Arrin's forces. Grank had determined that if Siv had fled, she would have gone there.
However, due to his exposure to the ember, Grank had a premonition that the Glauxian Sisters were under the influence of the Nacht'ga. Rorkna was no exception: all of the Glauxian Sisters were affected by this terrible spell. To break it, Grank needed to stab Rorkna with an ice splinter. Normally this caused death but in the case of an owl under the effects of the Nacht'ga, it would break the enchantment and all those affected by it would be restored back to normal. Grank succeeded in doing this after resisting Rorkna's fyngrot (caused by the enchantment).
When she and the other sisters of Glaux were restored, Grank lied and told them that an adverse weather condition had caused them to fall asleep. This lie stemmed from the fact that the Glauxian Sisters did not believe in nachtmagen. Grank asked Rorkna if she had seen Siv but she replied no. She did however mention the Ice Cliff Palace, a secret retreat that only trusted owls knew of.