When you think of high fantasy literature, Pokémon doesn’t exactly spring to mind. Considering the video game/ trading card game / TV / movie / toy franchise celebrates its 20th anniversary this month, however, it’s not exactly surprising that it has seeped through the cracks in our media and pop culture in a myriad of ways—including the multi-volume epic fantasy series. How did that happen? As it turns out, Dresden Files author Jim Butcher was challenged to tackle the inevitability head on. After six books in as many years, it’s safe to say he succeeded.

Back in the early 2000s, Butcher was discussing his craft in an online writers’ workshop. When the subject of good ideas vs. good execution was brought up, Butcher took the stance that any author truly worth their salt can create an enticing story with not one, but two terrible ideas. A challenge was put forth: write an interesting story mashing together Pokémon and the fate of a lost Roman legion. At this point, most authors would laugh heartily and go back to surfing the web. Ever the iconoclast, Butcher dove in head first.

The Codex Alera series launched just a few years later with first volume Furies of Calderon. The story borrows characters and general plot points from Republic-era Rome, mixing in a system of magic inspired by, yes, Pokémon. You see, the world of Alera is inhabited by furies—elemental spirits that inhabit everything from nooks and crannies to great volcanoes. When Alerans are young, they begin to manifest a connection with a personal fury, gaining the ability to call and control it with their minds (“I choose you, Alera!”). Depending on the element their fury favors, trainers citizens can benefit from the relationship in a number of ways—watercrafters can communicate over long distances, change forms, and control the water; woodcrafters can manipulate plants or create tools out of nearby flora. Naturally, these abilities can be dampened by opposing elements. If you’re buried in soil, for example, good luck calling your air fury. It’s not “super effective,” wink wink.

The genius of Codex Alera is that it takes inspiration for some odd places without leaning heavily on its sources. Even if you can’t tell your Casesars from your Pikachus, you’ll still have a grand old time with Furies of Calderon. Still, knowing the inspiration creates an extra layer of enjoyment, like being privy to an inside joke. As the six-part series matured over the years, its origins faded into the distance and the story took on a lush fantasy life of its own. The conclusion to the tale, First Lord’s Fury, was released in 2009.

Butcher had a successful career before Codex Alera, and he didn’t put down his pen after tackling Pokémon in Rome. A few years after Codex Alera concluded (and after a few more Dresden books), he announced a new series, The Cinder Spires, a planned nine-part epic set in a steampunk fantasy world. There’s no wacky origin story behind these books, though Butcher did describe it as League of Extraordinary Gentlemen meets Sherlock meets Hornblower…with goggles and airships and talking cats. First book The Aeronaut’s Windlass was released in late 2015. If it helps, you can pretend it was inspired by Final Fantasy. Or just, you know, read it because it’s that good.