So, i'm a little bit closer to finish my new project, sith acolyte's set. This is tutorial about its mask.
Materials you need:
1) PVC 1mm and 2mm
2) Plasticine
3) Super glue (lots of it)
4) Technical hair dryer (i don't know, if it has exactly this name) or torch to work with PVC. The first one is better, of course.
5) Transparent plastic (We name it "ПЭТ", so i don't know how to say it in English, sorry.. Very specific things to know)
6) Toning
7) Sieve
8) Newpapers and glue for papier-mache
9) Epoxy and some useless clothes
10) Silver and grey paint
11) Black acrylic paint and some alcohol or water for weathering.

Step 1: Choices

So, what i want to start with is.. Type of mask you're going to do. There are two completely different types of masks, i'm not writing about its style, about its patterns, i mean its shape.
The first one is a game-type, a 3d model from SWTOR. You can see it in the first photo in a little square. If you want to do this kind of mask, i think you won't have any problems with it, because it's really easy to find in Google a pepakura file and make a mask using standart technology. What about me, i don't like its shape, i've found it's not agressive enough, so i decided to do the second one.
The second one is a cinematic trailer variant (the first photo), i think it looks much better and more suitable for an evil character as sith acolyte is. So, i'm not the first guy who thinks this way, and Mynock already had done this mask before me (second photo). That's why I've decided to try to make a copy of his awesome work.

Step 2: Modeling

As I've already said, 3d model from SWTOR game is easy to find in Google, but there is no trailer-version models in free access. This is why i don't see another way except modeling it from plasticine or making a 3d model for printing. I prefer the first variant because i don't have a 3d printer and i'm a poor student :D
So, i made a base for my future mask using... Oh, let's name it "normal" parts from free pepakura files i found, because theese files are ABSOLUTELY different from Mynock's (trailer's) mask's shape. You can see theese parts, they're white cause they were made out of PVC. After that (sorry, i hadn't taken a photo) i just moulded from plasticine a base of mask, and it start looking closer to the originals.. I hoped so.

Step 3: Papier-mache

P.S i'd like to write it further as instructable, so.. i'll write "you" instead of "i", it'd be easier.

When you did a plasticine model, you'd have to "take off a paper copy" (Sorry, i can't name this process in another way). So, i think nobody needs in information about papier-mache and its recipe. All you need is to make your paper copy strong enough to not to lose its shape. After that, you need to put it off from plasticine model (to make it easier don't forget to put a first layer of papier-mache with water, not glue. This way paper copy won't glue to plasticine) and to make it stronger using epoxy and pieces of clothes. A lot of people prefer to use bandage or "fiber glass fabric (?)", but i found it's much easier and cheaper to use pieces of clothes. So, you need to prepare your epoxy and after that put it IN mask with clothes squares. Let every layer to dry, before putting a new one. If i explain this process unclear, please, read an article about it in the Internet, there is nothing hard, but it is probably the most important part of crafting mask. What is more, please, be careful and work with epoxy only on fresh air, because its evaporations are NOT good for your health.

Step 4: Patterns

When everything's okay, you have to putty it and to make the surface of your mask smooth and perfect. It is really long and boring step, but without it you won't have a normal product. There's also nothing hard, the only advice i can give is: please, avoid fragile filling, a filling for wood is the best (I tried a lot of types of filling, so that's just a personal opinion).

When it's done too, you need to think about patterns on your future mask. There are two variants, and you can see both in the first photo. By the way, theese masks have been made by Mynock too. I decided to do the second one, and this is time for my favourite part. So, wether you choose the first or the second kind of pattern, the technology is the same:
1) You have to draw a contour of pattern on your mask, but only on the one side of it.
2) You need to put there a paper adhesive tape and to redraw patterns on it.
3) You have to redraw it one more time, but finally on PVC sheet (i used 1mm, if i'm not mistaken. It was a long time ago in a galaxy far far away, so i've already forgotten what i used. Really. Although you can try both variants: 1mm and 2mm)
4) Cut the details and REDRAW IT AGAIN, but now it should be a mirror variant, because you have two sides of mask.
5) Glue them with super glue on your mask, but don't forget about symmetry.

This is what about pattern, also you need to make cheeks, but there is nothing to write about. Just draw patterns and make PVC details as usual.

Step 5: Oh, You're Still Alive!

After 15+ hours of work you'll finally have something, what looks not bad.. I guess. You have to cover it with primer, because you need a base for painting.

For lenses i recomend to use transparent plastic, made dark with toner and a part of sieve glued on it to make your mask look more agressive and scarier (2 and 3 picture)

Step 6: Final Step

When all of it has been done, you can paint your mask (grey and silver paints) and do some weathering (alcohol + black acrylic paint).
I've also decided to add some LEDs, but that's another story and i would tell it one day, when i made all the parts of my costume.

Anyway, thank you for your attention and sorry for mistakes, i tried to write as right as i can. Good luck in craft!

P.S If you have some questions, i'll answer with pleasure.