Question What power?

The biggest question is... does the character turn to smoke or does the character appear to turn to smoke. Shifting is, ultimately, limited by biology. Going to Jello mode (slime) is probably the furthest standard biological structure that you can get while keeping functional human thought patterns. Displacement or reduced density options in Warpers (as well as other plane shifting) could appear as smoke in the normal 3D world. Manifesting and PK variants could produce an 'outer' layer that is smoke... the physical body would still be there, but it would be cloaked inside the smoke cloud layer.

I think a combination of Warper/PK would be where I'd take it. Have the PK be a 'smoke kinetic' who can use their Warper ability to move through an elemental subplane between earth/fire/air (smoke) and draw smoke out from that plane for use in its PK shell and abilities. You could also go Warper/Energizer with the Energizer power source being the Smoke dimension also.

Anne wrote: Though as I said, depending on how controlled a shifter is and the level of their power, I wouldn't be at all surprised to see one be able to do this trick. I suppose that a manifestor could pull it off too if they were a high enough level manifestor. A mage?

Shifter - no. Trust me, Whateley Universe shifting CANNOT go that far. Whateley Universe Shifting can't even do some of the Sandman / Plastic Man / Mr Fantastick stuff that you see in Marvel/DC... because we have to account for biological processes / physics that they ignore. Mass limitations are a big factor, for example... there ARE some rare classes of Shifter that can alter their mass, but generally within strict limitations. And there ARE Shifters who can go to places that wouldn't be sustainable for human organs... but think about it, even going as far as 'slime' would require the ability to function without a nervous system transmitting perceptual and command data, without a respiratory or blood system conveying air/energy to the whole. And slime is still molecularly in contact within its boundaries. Smoke, by its nature, is diminishing dispersed solid matter carried by air. The closest I think a 'shifter' could ever get to smoke would be a spore cloud. But there can't be any spore cloud Shifters in the Whateley Universe. It'd be something like a Shifter 10 or 12.

Manifestor - no. Manifesting actually goes the 'wrong' direction to have someone turn to smoke. It adds mass (from ectoplasm), not removes it. You could create a 'false' image (a seeming) of someone turning to smoke... but it would actually not BE that person in the first place, just a manifesting created ectoplasm version of them that you then allow to dissipate in the form of smoke.

Magick - yes. But it'd probably be a pretty complex spell and thus require a lot of skill to perform at the expense of much Essence, moving it out of practical range of all but the most powerful. Of course, just how complex would depend on what it allows the recipient to do. If they can move like smoke (through small apertures), be undamaged by normal physical weapons (though at a cost of being at risk to wind/water), then it might be very challenging, Unless, as you say, its part of their nature (like an ifrit - a subtype of jinn and specifically a creature of smoke).

Sir Lee wrote: her shifting ability might be mystical in nature rather than the mutant Shifter power, no matter what categories the Wiki currently assigns her.

As I agreed above, unless its part of an innate ability for a creature made of smoke, like an ifrit.

A Shifter can't become a Sidhe either, typically. They can LOOK like one. But Shifting (as a MUTANT) doesn't involve a component of Essence... so just like it is very difficult (without powerful magick and a huge source of Essence - something that currently only rarely occurs, at the point where some mutants manifest) for someone to be changed from human to Sidhe through spell work, Shifters run into the same issue. Most Whateley Universe Shifting, after all, is mostly just manipulation of the appearance/shape of the flesh. Only the the powerful can shift to sustainable genetically whole alternate shapes... and only the absolute tops of the power can add power components (something that is part of the extradimensional construct of an individual as opposed to just physical genetics) or add or remove mass through the manipulation of ectoplasm.

But... if you ARE a Sidhe (or an Ifrit) and you have the ability to Shift (not common in Sidhe, but Ifrits and their lessers, jinn and such do it naturally... being creatures of smoke, it makes sense, really).

Lots of ways you could do that El... but the easiest would be for that Warping power to take the Warper through another plane instead of a direct A to B port (folding space). And then say that the power protects the Warper personally as they move through that 'subspace' but that anything else is affected by that energy. Supposedly, Nightcrawler's teleports work this way to a very slight degree. That's why there's the sulphur scented bamf associated with his ports. You could actually get nicely creative with the specific energy types or elements encountered in this subspace environment. But another X-men character, Illyana Rasputin (Colossus' little sister and one of Kitty Pryde's best friends... as a result of different time flows in hell and earth) as Magick had the ability to summon teleport disks... and her disks weren't A to B, she traveled through hell in between A and B.