Idris Costume breakdown. Because I know a lot of us are interested in creating this costume and it's kind of ridiculously complicated, let's all share notes. My impressions thus far, with quite a lot of pictures and a complete lack of technical terms. Personally, I'm not a perfectionist, so I won't worry about getting all the details right. But I do like to know exactly what I'm not doing. :P
So! Sexy the TARDIS costume, starting from the bottom up.
Boots: tan/light brown lace up mid calf leather boots, at least in the promo pictures. The episode is so visually dark that I never can see the lacing, in episode it almost looks like she’s wearing Uggs.
Tights: Seem to be white or off-white.
Skirts: Bottom most layer, a yellowish tan petticoat. We catch glimpses of it several times.
Then a couple layers of skirts which are what I would call Cadet Blue, probably in a fine silk, which is rather wrinkled. Each has a stiff ruffled hem several inches wide which is a lighter blue/grey color with bright teal stitching or trim at the edges. These skirts are about mid-shin length in front, almost floor length in back. They do not appear to be ruched up for ease or movement, they appear to actually be made shorter in front. Which means this can't be tied to any historical period, despite Gaiman describing it as a wrecked Victorian party dress. Well, can't be tied to any Earth time period. Just because she looks human doesn't mean the original Idris body was from Earth. ;) Which gives the costume designer a lot more leeway for creatively combining patterns.
ETA: Skirts may have been originally designed as overskirts with a bustle, or designed for a shorter person, with a train. She definitely appears to be wearing a small bustle in some promo pics, but possibly not in the actual episode. Undecided.
The back of the overskirt is deeply pleated for a very full skirt, and may include a middle back section of slightly darker material, or it may just be the angle of the light on the deeply pleated section.
The overskirt is a cobweb lace, net lace, or embroidered chiffon type fabric. It appears to be the same fabric as covers the upper bodice and sleeves, as such it seems the base fabric is very fine, nearly translucent so the color of the fabrics underneath show through. The embroidery is probably pale blue-grey. This skirt is the shortest and has unfinished jagged edges. It is very slightly gathered up at the sides, so that the front and back come to rough curved V shapes, with the middle longer than the sides.
Over that is a tied-on triangular hip scarf in a dark blue. It looks like a suede finish silk, or possibly a very fine nap velvet. The front goes into long braided tassels, which tie it on.
Bodice: The bodice is the lightest color, a taupey blueish grey.
The base is a very busy swirly jacquard or embroidered fabric. The jacquard almost looks like interlocking figure 8’s, which is appropriate as an eternity symbol. It will probably be nigh-on impossible to find anything even remotely similar. The only thing I’ve found thus far that is even reminiscent of it is this silk, which would have to be dyed and would still be only very vaguely similar, if you're across the room and you squint.
The upper bodice and sleeves are covered in the lace/embroidered chiffon fabric, which extends several inches past the base fabric at the wrist. It is torn and frayed in several places. This fabric covers the bodice from the neckline and extends over the upper bust in a wide V pattern, leaving the waist portion just the base swirly fabric. It has a ribbon trim at the lower edge and again midway between bust and neckline. There are two frayed silk bows at the front middle of the upper bust, one on each shoulder, and smaller bows where the under fabric stops midway between wrist and elbow. The underlayer of the sleeves seems to be a matching color fabric non-patterned fabric in a matte finish. The lace overlay comes to a wide V across the upper back as well.
No visible means of fastening, probably hidden hook and eye closure at the back? Or possibly the costume designer got lazy and used a hidden zipper along one side, the shoes certainly seem to have zippers up the inside.
ETA: Thanks to padawansguide for pointing out one moment when you can see that her bodice does somehow fasten down the middle back, as seen below. Could be a hidden zipper, but I'm going with hook and eye closures.
She also has tattered nearly translucent taupe colored ribbons in her hair, looping around the back of her head with the ends billowing out a bit in few places.
Her hair... dude, that's easy. That's what my hair looks like first thing in the morning anyhow.
ETA2: Fantastic huge promo pic here, click on it to make it giant. From that we can see a couple more details.
The hip scarf is definitely velvet, and appears to be one of those lovely color-depends-on-the-angle fabrics. Blue-grey-green-brown, aka impossible to match. You can also see a bit more of the waist seaming and see that it doesn't fasten in front because the ribbon trim is unbroken. Nice details on the lace overlay, too.
We can also see what seems to be a short cap oversleeve on her left arm, badly stained. This doesn't seem to be present on the right, which is torn up the sleeve seam on the back.
Right! What have I missed or got wrong so far?
Mods, may we please have an Idris tag?