Speaking of backgrounds...
In their native Feywild, pixies are commonplace. In the Material World, they are often associated with forest groves or flowering meadows, in much the same way nymphs are bound to lakes and streams, or dryads to trees. Tatterdemalion is an example of how the normally eternal and unchanging fey can be twisted by sympathetic resonance when something happens to the nature they are part of.
A long time ago, what is now the Gloaming Bog was a forest with a river flowing through it that lay 'close' to the Feywild and inherited some of its wild magic and exuberance. The pixie that became Tatter lived there, and was most likely a great deal like most pixies; carefree and prankish and capriciously merry.
But the planar alignments shifted, bringing the Plane of Shadow into conjunction. Clouds gathered and rain fell. The river overflowed its banks and turned the forest into a wetland...then a marsh. As the Feywild receded, and the Shadow took sway, the pixie of the wood developed a black mark on her left hand and changed along with her landscape. She became what she is now; the Lady of Wisps, the Sobbing Shadow...the Tatterdemalion.
Despite her gloomy demeanor and occasionally sharp, pointed sarcasm, Tatterdemalion did not turn evil as many believe. Her many charms and ensorcellments turned to spells of darkness and fear...but they are still simply tools she uses to try to make the world better (even if she claims not to believe such a thing is possible). While it is tempting to regard her story as tragic, she does not see it that way. She is what she is, and finds the prospect of becoming 'fluffy and happy and annoying' again just as abhorrant as she would have found becoming this way before.
Her specialty is now as it was before; clever ruses and deceptions using a combination of arcana learned from witches and mages seeking knowledge, or to tap into the power of the planes, and fey glamour to decieve the senses and mislead the mind. She can also draw on the power of her Mark to manipulate Shadow essence in certain ways, though this is more recent and less developed for her.
Tatterdemalion joined an adventuring group shortly after leaving her swamp, and for a time traveled with them. She shared her magic in exchange for protection and cooperation, and gathered enough power to return home and vanquish a monster that had forced her out. This unusual display of pluck gathered her the attention of the Court of Stars...and for years she served as a spy and double-agent among the Unseelie; taking advantage of her reputation and sinister powers to blend in.
Finally her mission was over, after many intrigues and thwarted schemes. She was free to return to her bog...but found it felt a bit small now, after she had seen so much of the world. So she set forth to find her old friends once more.
(Agh! I may have to get Arcane Familiar soon and get a Wisp! It'd work well with her blink dog too! In fact..hey,Mr GM...what do you think about 'reskinning' the blink dog as a kind of willow-wisp type thing? Same stats, but just looks like a glowing ball instead of a dog? Damage maybe becomes Lightning instead of normal? Or not...whatever on that. But that, plus the teleport powers, would work perfectly with Tatter's concept.)