For a while now Wizards of the Coast have been releasing free material for D&D 5th Edition based on the settings they created for Magic: The Gathering. In order to use these worlds you just need the free D&D Basic rules available from the official D&D site and perhaps a copy of the gorgeous “Art of …” artbooks containing artwork and background information on these settings.
Even back in the 90s when I first played Magic: The Gathering I thought it would be cool to be able to roleplay in the worlds hinted at on the cards. Sometimes an image or a quote summoned up whole worlds with strange artifacts, bold heroes and impressive magic. And finally WotC has actually done just that and released free material for three of the Magic: The Gathering worlds: Innistrad, Zendikar, and Kaladesh.
Unfortunately finding anything on the WotC site is a chore, so I did the work for you and provide you with the direct links to the PDFs below, accompanied by a quote from the world descriptions.
Plane Shift: Innistrad
”On the plane of Innistrad, horrors stalk the shadows and scratch at doors in the night. Humanity is beset on all sides: vampires thirst for human blood, werewolves live for the thrill of the hunt, the restless spirits of the dead haunt the living, and no corpse is safe from reanimation at the hands of cruel necromancers or cunning scientists. Only their grim determination—and their staunch faith in the protection of their patron archangel, Avacyn—has allowed humans to survive in this nightmarish realm.
The people of Innistrad are surrounded by monsters. Almost without exception, anything that is not human, whether it’s a rat or an angel, is a potential enemy. Even the traditional allies of humanity—from angels and gryffs to herons and hounds—are unreliable at best, as the madness that grips the angels seems to seep into every living thing. And at the same time, humanity’s age-old enemies grow ever more dangerous.”
Plane Shift: Zendikar
”Zendikar is a dangerous world of lethal risks and priceless rewards. From the perspective of its inhabitants, it is a hostile place that seems to be actively trying to kill any creature that has the audacity to live there. The danger is unrelenting. Precarious terrain, cunning predators, and natural disasters on a massive scale all present a constant challenge to survival— as do the unpredictable ripples of change that wash through the plane, known to its people as the Roil. Even the mana that suffuses the land is wild and hard to tame. It feels almost alive to those who wield it, and sometimes causes the land to manifest magical effects much like spells. Zendikar is a plane of deadly peril, but the denizens of that plane grow up strong and resilient, prepared for the dangers of the only world they know.”
Plane Shift: Kaladesh
”Kaladesh is a living work of art—a vibrant, beautiful plane where anything is possible. Optimism, innovation, and the spirit of creativity fuel an intoxicating renaissance of invention and artifice across Kaladesh. Its inhabitants frequently assert that “anything can be built,” and brilliant inventors seem to prove that saying every day. Clockwork automatons walk the streets, acting as servants and bodyguards, soldiers and sentries, mounts, and even pets. Soaring airships provide transport both within and between the cities and villages of the plane, and carry prospectors high into the sky to draw on limitless reserves of magical aether.”
The setting documents are meant for D&D 5th Edition, but I am pretty sure you can easily convert the material to older editions of D&D or simulacra thereof. Enjoy!