A common sub-genre, Crossworlds Fantasy is often used in conjunction with other sub-genres. The sub-genre features a protagonist from the 'real' world—that is the world that we all know. This person is somehow transported to another world where he or she embarks on an heroic adventure to defeat evil. The action of the story does not really begin until after the main character is transported to the magical realm. The struggle between good and evil or light and dark is the prime point of conflict in Crossworlds Fantasy. Indeed, the main character is likely to have skills unique in the magical world that make them the key to defeating evil.
Crossing between worlds is not a common occurrence. Not everyone has the ability to travel between worlds. Sometimes characters cross between worlds accidentally and sometimes they are summoned there as champions.
Allegory and metaphor are frequently used in Crossworlds Fantasy because there is an automatic comparison between our world and the magical world, or worlds. The relationship is ripe for storytellers—and lets writers create things that stand for other things. For example, the character of Aslan in C.S. Lewis' The Chronicles of Narnia is an allegorical character representing Jesus. Because of these features, Crossworlds has the potential to become quite philosophical.
Crossworlds Fantasy is very similar to Portal Fantasy and often overlaps. But it's not necessarly the same.
Crossworlds Fantasy vs Portal Fantasy
Crossworlds Fantasy usually features a protagonist who 'crosses over' from the real world to a fantasy world. Portal Fantasy may include Crossworld fantasy but the emphasis is on using some sort of portal/window/door by which the protagonist crosses into the new world. Portal Fantasy may NOT always feature characters from the real world to a fantastical world. It may in fact be a portal from one fantastical world to another more fantastical word.
The biggest difference however is that Crossworld Fantasy may include crossing over to not only different worlds but TIMES as well while portal fantasy involves travel to another world, not necessarly the same world but different timeline.
The definition between the two sub genres, as stated, is pretty similar. For many purposes, portal and crossworld fantasy can be considered the same. But if you get picky, there are some subtle differences.
Increasingly High. On our world, there is no magic. But on the other worlds, magic is integrated into the environment. So, the protagonist (who tends to be from our world) becomes increasingly exposed to magic and its possibilities as he or she delves deeper into these other worlds.
Moderate. Ideas are not necessarily grand in Crossworlds Fantasy, but there are some strong social commentaries. Because the protagonist tends to be an outcast in our world, he or she offers some insight into our social structures.
Crossing between worlds creates the possibility for allegory, which of course allows for some social commentary. People, events, and places in the magical world mirroring the 'real' world is a common occurrence, which is just one means of social commentary. Protagonists often learn something on their journey between worlds that they are able to apply to their life in the 'real' world.
Moderate-High. Protagonists are often a kind of outcast in the 'real' world—they don't quite fit in, but they are about discover something amazing that'll make up for that. The protagonist will become a hero by the end of the story and the reader will have experienced the journey from ordinary to extraordinary. All through this journey the reader will get to know the protagonist. This does not mean that all characters are as well developed.
Moderate. Plot is a driving force for the Crossworlds story. However, the overarching plot is predictable: seemingly mundane dud is transported to a magical world, dude discovers some kind of special ability, dude vanquishes evil, dude returns home having learned some valuable lessons.
Moderate. There is a battle between good and evil raging. While all roads are leading toward an epic battle, the violence is not usually gritty, graphic violence. Indeed, the protagonist is able to win not necessarily because of violence (although that plays a part) but because of the protagonist's brave and true heart. This is especially true of the YA books.
Mundane Fantasy. Crossworlds and Mundane are very similar, the defining difference is that rather than our mundane world having magical elements, Crossworlds Fantasy has other worlds that are magical and ours remains mundane.
Portal Fantasy. The main difference between Crossworlds and Portal is that portals connect spacetime, so you may travel to alternate dimensions and time periods—not just other worlds. But, this is a fuzzy line.
Urban Fantasy. Both Urban and Crossworlds Fantasy share the realism of our world—it's just that Urban Fantasy stays in our world.
Young-Adult Fantasy. Many Crossworlds fantasies are written for a YA audience.
By C-S-Lewis. A classic piece of Fantasy, these stories are all about adventures in the magical land of Narnia.
By Ursula K. LeGuin. The beginning place is Tembreazi, an idyllic world of eternal twilight. Two people find each other here and join forces to seek out the shadow threatening to destroy the world, and fall in love along the way.
By Roger Zelazny. There are two worlds in this book one ruled by magic and one by technology. One infant is exchanged for another in order to maintain balance between the worlds—but when one seeks to build war machines the other must return.
By Guy Gavriel Kay. In this trilogy some University of Toronto graduates are transported from a Celtic conference to a magical world where they must against the darkness.
By Poul Anderson. Dark forces threaten the world of men. Legions of magical creatures are in the mood to do some overthrowing. One man just might be the legendary hero who can save it all.
By Stephen R. Donaldson. This two-part series with a man crashing through a woman's mirror in order to find a champion, a champion to save his kingdom from evil.
By Philip Pullman. The second book in the His Dark Materials series introduces readers to Will who is from our Oxford. Will and Lyra travel worlds and together. Yet another example of Crossworlds meant for YA audiences.
By Kevin Gerard. A five part series intended for a YA audience. Conor has suffered a great loss and he seeks answers to his pain, the creators of the Crossworlds pluck him from Earth and send a mentor, a flying talking magic wielding cougar.
By Neil Gaiman. An example of the crossover between Urban Fantasy and Crossworlds. An ordinary man is transported to a world of shadows and darkness and must make his way home.