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.
I think it was not uncommon for druids – and other mystical figures in folklore – to appear before others in magical disguise. Glamour, after all, is heavily associated with the fey, which are in turn tied to the natural world and the same sort of mythological background as druids. Further, as protectors of the natural world, druids have to assess potential “civilized” threats – appearing as a wanderer, sharing a campfire, gives you a good sense of whether the new people are going to be a problem.
Mostly, though, it just seems to play up the druids’ mystical angle. They know things, deep lore of the natural world but also about the comings and goings around them that they couldn’t possibly know. They have animals as eyes and ears but sometimes they need to see and hear for themselves. I think it is an appropriate, flavorful feature. And unlike most of the druid’s class features, I don’t think it’s overpowered.
Also, be careful about thinking too much about druids as being of or defending nature, because that was not really their historical or narrative role. The word “druid” itself means “oak-knower,” where oaks are symbols of all things ancient and deep. The druids were mystics, wise men, and priests. They drew their powers from the natural world, but much of their power was knowledge as much as it was magic (of course, at the time and in the myths, these were often the same thing). Any magic they had came from their knowledge of the nature of a world that had magic built into its very bones.
In role, they may have often been apart from society, but they were still very much human and very important to society. Their counsel was sought out in all things mystical and natural, which is to say everything that the common man did not understand. They were often highly political, kingmakers or rulers themselves as high priests. They were protectors of the old ways, which included human custom as much as it did the ancient natural world.
Best Answer
I believe you're thinking of the Eidoneus, a "lumina" from the Legends of Avadnu book. It's a CR 31 Good Outsider and it's very blue and white. The lumina are "extraplanar beings of purity and light from a distant realm, as alien as they are good...Lumina almost never leave their homeworld willingly...To a lumina, the mortal world seems an almost intrinsically evil place, where only the most pure individuals show even a glimmer of goodness." So it's less that it's painful for them to be on the material plane, and more that it's horrifying and evil.
The Eidoneus is the one with the aura of regret.
The world is called Avadnu, and Legends of Avadnu has a section on page 22 explaining how lumina fit into Avadnu. The setting itself is called Violet Dawn: the Time of the Unraveling.