[RPG] What was this Magic the Gathering RPG I remember

If your timing is right, and your terminology close, then what you might have seen is an Everway sourcebook. Everway was a card-based roleplaying game released by Wizards of the Coast concerning people known as spherewalkers who can journey from world to world. It could easily be mistaken for a Magic: the Gathering RPG.

To be clear, however: no official Magic RPG exists, or has existed. However, Dungeons & Dragons 5e has bridged the gap between MtG and D&D. Here's an official writeup of Zendikar as a D&D setting, straight from Wizards of the Coast. Here's one of Innistrad. But the biggest change has been the release of the Guildmaster's Guide to Ravnica, which brings one of MtG's signature worlds into D&D5E.

Ryan S. Dancey has, on Reddit, posted what can be seen as a comprehensive supplement to this answer.

Hi! I was the brand manager for Dungeons & Dragons and the VP of Tabletop RPGs at Wizards of the Coast from 1998 to 2000. I can answer this question.

There were plans to do a Magic RPG and several iterations of such a game were developed at various times. After Wizards of the Coast bought TSR, there were discussions about making a Magic campaign setting for D&D.

After the release of 3rd edition, we had planned to do a Monstrous Compendium for Magic monsters which would have been a tentative cross-over product to see what the interest level was for such a book.

In the end, the company made the decision to keep the brands totally separate. Here's the logic.

D&D and Magic have fundamentally incompatible brand strategies. This is was once expressed as "asses, monsters & friends".

• D&D is the game where you and your friends kick the asses of monsters.
• Magic is the game where you kick your friends' asses with monsters.
• (Pokemon, btw, was the game where the monsters, who were your friends, kicked each-other's asses.)

There was no good reason to believe that a D&D/Magic crossover book would sell demonstrably more than a comparable non crossover book. And such a book should be priced higher than a generic D&D book - in the way that Forgotten Realms books cost more than generic D&D books (that's the price premium for the brand). There's a fear in sales that the higher the price, the less volume you sell.

The brand team for Magic didn't want to dilute the very honed brand positioning for Magic as a competitive brand, and the brand team for D&D didn't want to try and make some kind of competitive game extension for D&D.

In the end, I think the company was well served by this decision. It eliminated a lot of distraction and inter-team squabbling at a time when neither team had the resources to fight those battles.

Today you might argue there's a different reason. The #1 hobby CCG doesn't want to be entangled with the problems within the D&D brand.

Other Wizards of the Coast employees chime in on his Facebook page.