Saudade

Moving along the wastes of the world, you can find Saudade on occasion. Known practically as a legend, Saudade is a shapeshifter and engineering specialist.
Saudade specializes in all manner of healing, genetic modification, and is one of the only people who can adequately inject and synthesize the retrovirals needed for biological upgrades/changes. She rarely charges cash, if she did, only few could afford it.
No, Saudade trades in only two things, skill, and will.
Using a combination of mimicry, mysticism, and a permanent version of polymorph other, Saudade will literally take your memories of certain skills from you, removing your ability to use them down to and including the muscle memory. Although the skill can be retrained, the attribute lowers by 3 points, and the skill associated with it is gone. She only accepts an attribute twice the level of the bonus afforded by the new modification, though she'll lower the cost by 1 if the memories are of Sigil, city of doors.
After taking these abilities, Saudade immediately injects herself with the resulting serum, gaining all of that knowledge. Though no-one has ever actually seen her use her abilities for anything other than modifying others, it is presumable that her combat skills must be godlike.