Maguffins for speculative fiction
Alfred Hitchcock named this narrative device. It is something which drives the plot forward and gives the story purpose. And yet, as the man himself said, "The main thing I've learned over the years is that the MacGuffin is nothing." It doesn't have to be something the reader cares about, all it needs to do is to act as the energy force in the story, giving the characters a purpose. Hitchcock claimed his best maguffin was in his North by NorthWest and boils down to the selling of state secrets. This was his 'emptiest' maguffin because the entire film focuses on the pursuit of Cary Grant's character who is trying to discover the truth about James Mason's character.
Do you recognise all the maguffins in the picture? There is the crystal skull, Thanos' glove with the infinity stones, the alethiometer from His Dark Materials, LOTR's ring, spice from Dune, the Elder Wand, the Iron Throne from GoT, the Tardis and the Hitchhiker's Guide. All of them things which drove their respective stories forward.
If you're looking for some inspiration, here are some more maguffins you might want to consider for your story.
The Magical Mineral
This maguffin has been used in lots of ways. It's comes in the form of Kryponite to spoil Superman's day. As Unobtainium it creates conflict in Avatar. Grind it down and you get The Spice in 'Dune'. It earns the title in The Dark Crystal where elflings need it to maintain peace.
If you are into alternative therapies you'll know that different minerals are believed to possess properties which affect our bodies. These crystals offer all kinds of story opportunities if you take these qualities further. For instance I've used amethyst as a means to control minds. Jade has a variety of purposes in Chinese medicine. It's really worth researching what crystals and other minerals can do for you.
The Magical Portal
I'm a big fan of this maguffin, as you'll see in many of my short stories. They are the means to travel from one location to another. However, do some research and you'll find locations in the real world where there are legends of such things. In the UK, it's worth visiting Glastonbury to learn about gateways to fairyland. The myths surrounding such maguffins offer variations that make for great stories. For instance, time can work differently. If you're a fan of Stargate you'll know that portal was linked to cultural myths and opened up a network of portals to different worlds. Being a door (as is explained in Avengers Assemble) it can open two ways - it's a means to invade. Wormholes or event horizons may offer scientific explanations!
The Magical Device
This is the AllSpark used in the Transformers franchise. Usually the identity of such things is not understood by its owner/discoverer. The first act of any story deals with how its strange behavour manifests and drags the hero (unwillingly) into the story. JK Rowling used this maguffin all the time, the Elder Wand is one example. In Dr Who it's the Sonic Screwdriver (which has increased its abilities since the second doctor started using it in Fury from the Deep). These devices are perfect for when you write yourself into a corner! But that also means you need to avoid relying on them for the same reason, these maguffins can lead to some very contrived plots!
People as maguffins
The Last Airbender in the M. Night Shyamalan film is a maguffin. It's a popular device for this writer/director, in Sixth Sense the character of Cole Sear (played by Haley Joel Osment) is one too. The Eddie Murphy film it's the titular character in the The Golden Child.
In fantasy it's a well-used device. The Chosen One premise leads us to stories where the hero must rescue a character with special abilities or purpose or the hero is that person and must strive to complete their mission against all odds. In The Matrix, it's Neo, of course. They are a character who may be single-minded in reaching their goal but you can have fun when they are completely unsuitable - Buffy, the Vampire Slayer is such an example. Joss Whedon's character, a shallow teenage girl and cheer leader has to be prime candidate for this premise. So utterly unsuitable for something so violent/horrific.
Who should wear the crown? Game of Thrones sustained eight series on TV and (when completed!) there will be seven novels by George R R Martin. It's a great maguffin to deal with betrayal, ambition, love and political intrigue. But there are other maguffins you can wear that serve other purposes. JK Rowling, along with others, has used the idea of the 'cloak of invisibility'. It's a feature in Brent Week's Lightbringer series (which I love!). When we're talking cloaks though, my favourite has to be Dr Strange's in the Marvel comics - not only does it allow him to fly but its sentient too! What you could do with that, eh?
In the Wizard of Oz Dorothy wears the ruby slippers which transports her back to Kansas but the footwear is jealously sought by the Wicked Witch of the West - even though red and green tend to clash. There are rings, amulets, talismans to include in this category and they cover probably half the fantasy genre of stories in some shape or another!
The great thing about this maguffin is that, being portable and wearable, ownership can change. They can also work as metaphorical images too - crowns represent power of course but cloaks (invisible or otherwise) can provide mystery and even identity. (Where would Batman be without a cape that makes him look like a bat?)
I hope my catalogue of maguffins offers a few ideas for your stories. The danger is to use one in an unoriginal way of course. But research is useful for defining it in a new and original way. For instance, a ring with a piece of amethyst could provoke reactions from other people (controlling their mind?) but it might mean the amethyst is very rare in your world and it is the only piece left to priceless. I hope I've shown here that Hitchcock may have been wrong - maguffins aren't 'empty', they can contribute to a highly original premise that makes your book truly unique.