Twixt Firelight and Water is a novella which ties in with the Sevenwaters series, and should be read before Seer of Sevenwaters. It was published as part of Legends of Australian Fantasy edited by Jack Dann and Jonathan Strahan, and is also available in Prickle Moon, an anthology of Juliet Marillier's short fiction.
The story is fast-paced compared to the first three books of the Sevenwaters series, and reveals the true identity of Ciarán's raven companion, Fiacha. He is in reality Conri, the elder son of the Lady Oonagh by an unknown father, and therefore Ciarán's half-brother. He helped his brother escape from their mother's cruelty, and was subsequently transformed into a raven by the sorceress on the day he was to be married. The curse had a limit of fifteen years, provided nobody recognised Conri and called him by name. Should anyone discover the truth before the time was up, he would remain trapped in that form until a woman of the Sevenwaters family agreed to marry him. Ten years later, his sweetheart, Lóch, was fatally wounded, and when he flew to her side in distress, she saw him and spoke his name with her dying breath, sealing his fate.
Many years later, Aisha, Padriac's eldest daughter, an independant and adventurous woman, decides to travel to Erin and visit her father's family in Sevenwaters. During her journey through the forest, she encounters Ciarán, who is enjoying a few days respite from his druidic duties, accompanied by Fiacha. He agrees to lead her to the keep, as she has become lost in the forest despite being a descendant of Lord Colum. However, they have still not arrived at the end of the next day. That night, Ciarán reveals Conri's story to Aisha in a vision, and although she has never wished for a husband before now, she has also never backed down from a challenge, and she realises that she might be Conri's only hope. Even after Ciarán tells her she will have to make a permanent vow to ensure the curse is lifted, she still accepts. The ceremony is performed, and Conri is freed.