In The Enchanted Island of Yew, L. Frank Baum wrote about a fantasy land that bears some resemblance to his other locations, but has no clear connections to them. The story involves a female fairy who is transformed into a male knight named Prince Marvel for a year, and travels around the island doing good deeds and making the place less barbaric. The name for the entire place, the Isle of Yew, is actually a pun, but I have to admit I didn't get it until I had it explained to me. It's basically the same joke that Piers Anthony would later use with Isle of View, although he spells it out more directly. Anyway, the book ends with a flash-forward, which isn't unusual for Baum, but is still weird in a way. One hundred years after the end of the main plot, the Red Rogue of Dawna escapes from his prison in a magic mirror, and finds that the island is now civilized and no one remembers him or Prince Marvel. Does this mean Yew has become part of the civilized world, or just that it's not as magical as it was in the past? It's hard to say. As I said in this post, Baum eventually tied most of his fantasy lands together, but never did this with Yew. That could just be because his map shows only a tiny bit of the ocean, but it's possible there's some other reason he didn't include it. James E. Haff and Dick Martin's map does include Yew, placing it to the east of Hiland.
Yew has been used in a few recent Oz books, but never in a particularly major role, perhaps because today's authors aren't totally sure what to do with it either. In Do It for Oz, Chris Dulabone describes the civilized island with his typical sense of humor, claiming that the fairy bower in the Forest of Lurla had become a parking lot for a fast food place, and the Baron Merd's castle an apartment building. The Red Rogue soon leaves the island, though, so we don't see that much of Yew. And in The Royal Explorers of Oz, Prince Bobo visits nobles called Nerle and Seseley, only to find that these are actually titles and the two are not the same characters who appeared in Baum's book. There's also still a King Terribus in Spor, but he's a descendant of the original Terribus whom Prince Marvel assisted. I wonder if any of Terribus' descendants inherited his legendary ugliness. Yes, Marvel changed his appearance so he would be good-looking, but was that change genetic or merely cosmetic? There's also a hint that the pirate captain who steals Bobo's ship could be the Red Rogue, although it's left ambiguous.