The Ragwitch 2 - moral development.

A story with a portal to another world borrows directly from C S Lewis's Narnia books. The Lion, the Witch and the Wardrobe even has the evil witch/queen. Written in the 1940s and published in 1951, that story starts with the blitz and evacuation. The witch/queen's destructive domain represents the Nazi preference for power over ethics and her defeat by children is a moral call to arms. C S Lewis in turn borrowed the idea from George Macdonald, whose forays through the portal are highly symbolic - Phantastes, and Lilith towards the end of the 19th century. Macdonald took this idea from German developmental novels. I take it therefore that adventures in parallel worlds represent inner struggles from which personal growth develops. Most deal with struggles between good and evil, wisdom and folly, and loyalty and betrayal.
In The Ragwitch, evil is a reality which can overcome decent people through fear and powerful magic. It exists 'out there' and should be left severely alone if disaster is not to occur. Once awakened, it cannot easily be put back to quiescence. In real life, rage and hate erupt from time to time but are human choices rather than demonic possession. The genocides of the past century have been deliberate political strategies by powerful groups, exerting power through a mixture of fear and persuasion. Humans are apt to lose moral constraints very easily, particularly if the 'other' can be dehumanised as 'the enemy' or 'another race'. Evil is a human direction or set of choices in which selfishness and greed are promoted rather than the common good.
Stories such as the Ragwitch emphasise loyalty to decent people, compassion and the importance of heroic resistance. These are important lessons for children (and adults) to learn.