Based on the images shown in the Lighting Script in The Art of Legend of the Guardians: The Owls of Ga'hoole, it appears that the scene was set to take place before Noctus went hunting, which is the movie's current starting point.
The scene is narrated by an unknown individual. The beginning scenes show the brutality of the Pure Ones, chaining owls by the talons, slicing off the feathers of a Burrowing Owl (who some readers hypothesize is Flick) and a mother owl shielding her owlet while crying. The scene then cuts to a blizzard, and Lyze of Kiel, leading the Guardians, flies towards Metal Beak, leading the Pure Ones. At this point, Metal Beak still has his beak. Metal Beak and Lyze of Kiel are shown fighting, and during the battle Lyze's toe is sliced off, falling towards the ground and becoming lodged in a rock. Lyze then flies up above Metal Beak and clubs him in the face with his battle claw, shattering his beak.
The scene then cuts to Soren, Kludd and Eglantine in their hollow, and it is revealed that the narrator was Noctus telling his children the story. Soren doesn't want Noctus to stop the story, but Noctus says he'll "finish this another time."