The fourth book in the series about Niel. The first one is here: Days and months passed, and the nine-color door continued to hang high in the sky. Ordinary people have already stopped paying attention to her, it’s as if she has fallen out of their visibility zone, and has become something ordinary and familiar. Not many knew what the appearance of this sign foreshadowed. Invasion. The demonic race, the second in Rönne's list, has officially entered this world.