The taking of Crow's Nest occurs amidst the Landing of the Golden Company.
In his campaign to place Aegon Targaryen on the Iron Throne, Jon Connington joins the sellsword Golden Company in invading the stormlands. Their Volantene fleet is scattered by a storm after Lys, and only six of the sellswords' ten ships arrive at the rendezvous near the rainwood in Cape Wrath, land formerly owned by House Connington. The gathered force is not quite half the Golden Company's full strength of ten thousand.
Jon leads a quarter of the available strength to take Griffin's Roost, the ancestral seat of the Conningtons, of which he was lord before being exiled during the War of the Usurper. Simultaneously, Ser Tristan Rivers sets off to take Crow's Nest, seat of House Morrigen, while Laswell Peake marches for Rain House, stronghold of House Wylde.
According to a semi-canon source, Lester Morrigen, the Lord of Crow's Nest, has followed Stannis to the north. However, the current location of his brother and heir, Ser Richard Morrigen, is unknown. Richard may be in charge of the castle during Rivers's attack.
During her journey to meet Aegon Targaryen, Princess Arianne Martell learns that Crow's Nest has fallen to the Golden Company.