Each Magic set takes place on a certain plane, which is like a planet. Some characters are planeswalkers, and can travel between planes, but since most do not, the tribes and wildlife on each form unique civilizations. The spirit of each plane is expressed through the art direction for the cards in the set — and the art has often been quite impressive. It’s rare for an image to be highly abstract or symbolic, but they are nonetheless very pretty and, sometimes, iconic.
Once, Magic sets were accompanied by novels that detailed the exploits and struggles of the characters and communities depicted on the cards (characters who are also referenced and quoted in the flavor text printed on some cards). These days those stories are explained in a weekly series of blog posts. The ways in which the other-worldly tendencies of the alien races and characters are expressed through their mechanical abilities is idiomatic and resonant; the plot makes card functions easier to remember, and gives hints about how to use them wisely.
There are also details about the story that not revealed, but are foreshadowed in the art. Sets are designed for several years before their release, so their overlapping schedules enable integration from each artistic and game design direction to the next. The story is customized to the mechanics of the set, and the details of each plane in the multiverse often drive decisions about which get printed, to best explore the types of gameplay that research and intuition show are the most fun, fair, and popular. When Mark Rosewater explains his process it’s interesting to note that while much of his design is based on what people tell him they like and what his team enjoys, it’s always rooted in the flavor of the plane they’re depicting, and many of the gaming decisions are true to its nature.