Please pardon the fanfic. As always, Wizards and Noel, thanks for the inspiration!
Mycostone
The nature of a planeswalker is that of a being intimately connected to and in touch with the energies of existence which envelop and bind all things, one to another. All the power of a planeswalker, their very life, is defined by their relationship to and control over the threads of mana which weave reality together.
At least, such is true for most planeswalkers. Not so this one. He loathes mana. He is allergic to it and to the very fundaments of life itself. Merely living among the energies of the world leaves him distracted and irritable, nauseous and feverish, his body aching and his skin sore with hives. Magic has caused his entire life to be defined by inescapable illness.
But he has a plan. He has found a small, nearly empty plane, almost all secluded steppes and featureless plains with only a handful of ancient ruins, untouched for eons, dotting the blank uniformity. The immense age of the plane and the untold millennia of its abandonment has already left it drained of much of its natural energy. Unsatisfied with this, however, the planeswalker has also buried nodes of enchanted porphyry in various places around the plane which are slowly, imperceptibly, draining all the life's essence out of the few native creatures that still call the plane home. Soon, the plane will be scoured of all but the faintest hint of mana itself. But the planeswalker will go even further.
He has acquired a small sample of something precious. A synthetic fungus, mycosynth, quick-growing and nearly devoid of mana properties itself. Where mana dies, mycosynth thrives. He has planted cuttings of this mycosynth all over his pocket plane and now simply plays the waiting game for it to devour all that it touches. And when the entire plane is made sterile mycosynth, he shall summon an eternal, stony silence upon the world and purge it of all mana once and forever. Then, will he finally be free of the curse he could cure by no other means.
Self Loathing
This planeswalker, too, bears a curse, although one he is proud of. A fire elemental, he comes from a plane where his kind is an endangered species. The dragons of his world nourish themselves on ash and flame and their favorite cuisine is elemental flambé. The elementals are cursed to be hunted by all that find them, either by the dragons themselves or by those who wish to curry favor with the wyrms.
But this planeswalker's people have long fought the dragons and hunted them in return. They use the strength of their curse to their advantage and know how to manipulate the dragons with its power, even to turn them against their own scaled kin. So it has been for generations upon generations.
Until this planeswalker's spark ignited. When he finally returned to his homeplane, he gathered his people about him, many several lives removed from the peers he had once known in his youth, and told them his plan. There were worlds beyond this one. Many worlds. And they were to escape to them. He would lead them.
Many refused to leave. No matter how dangerous and unwelcoming, this world was still their home. But nearly as many chose to follow the planeswalker into the unknown.
Now, he and his kin wander the multiverse as a free company of dragonslayers and dragonslavers. Where they find a need for their services, they ply their trade at a high price, but they always deliver on their promises. And where they find no need for their services, they ply them anyway just for the pleasure of the hunt.
Give up the Ghost
Despite what some would have you believe, transfiguration is not an easy discipline. One can't simply wave a wand around and transform a teacup into a mouse or something. One must have detailed, exhaustive knowledge of every element and component that comprises both forms and must also know the means of replacing each element with its precise, respective complement, in what order and in what configuration.
This planeswalker knows all about that. He has spent the majority of his life studying the nature of transfiguration. He is very familiar with what it means to reshape a thing in its matter and essence and also with what happens when the process is reversed.
More recently, however, he has become deeply fascinated not so much with the transformation of one thing into another, but of nothing into something or even of something into nothing. This is a new frontier for him, one which he is highly excited to explore.
Unfortunately for many of his early test subjects, they have fared less well than has his own enthusiasm. His chambers of manipulation are now haunted by the mad phantasms of unsuccessful experiments (or, perhaps, highly successful, depending on the definition of the experiment) and great, slavering beasts keep unexpectedly bursting through of the surfaces of his breeding pools at the most inconvenient moments.
He's even started to see ghosts, or perhaps things even less substantial, flitting in and out of the branches of his private orchard. He should really stop letting all these minor concerns distract him from his work, he thinks as he walks back down into his woodland lab.
But first things first, he says to himself. I'll have to take down all these mirrors all over the place. I don't even remember what experiment I hung them for anymore and I always feel like I'm being watched through them when I turn my back.
And he thought that to himself anew every single day until the ghosts finally showed him just how far his work in the transfiguration of matter into nothingness had come.