The creators of Fable initially envisaged it as a magic dueling game where you shaped the world around you, creating forests, volcanoes and lakes before slinging spells at your enemy, according to Dene Carter, one of the original developers.
At that point in time, Fable was called Wishworld, and YouTube channel People Make Games managed to get its hands on a playable build. The build was limited and looked generic, but the concept sounds fascinating, and the channel interviewed Carter to get more of a sense of what the game would've looked like.
In Wishworld, the player would pick a character archetype with a particular magic specialty. Then, they'd be placed in a blank, dark void, and from there they'd generate the environment around them. Depending on their character type they'd create rivers and forests, mountains and volcanoes, or vast lakes. They'd also summon creatures and find orbs that would charge their spells.
The enemy would do the same, and you'd be able to see them working their magic in the distance. Eventually, once you'd created your own world and gathered your spells, you'd strike out at the heart of the enemy's newly-created base, trying to defeat them. Carter describes a situation where you'd see eruptions of fire in the distance—to counter, you might create a lake, summon mermen and water spirits, boost them to five times their normal size and ride into battle on the back of one.
The idea was never picked up by publishers and Carter's team, with the help of Peter Molyneux, refined Wishworld into what eventually became Fable. The whole video, below, is worth a look if you were a fan of the RPG.