I'm still drawing with some doubts along the way
Today's advances: I have defined a little more the body of the girl adjusting some parts (the right hand to a more natural posture). I have opted for option 3.
I still have to decide how to draw head: helmet? hair color?
I admit suggestions.
Today's advances: in the end I opted for single hair, I think it gives more movement to the figure. I have also defined a little more the figure of the other girl. This girl is going to be from the earth faction. This weekend I will think about this costume. I know I'm going to do hair with leaves and wear tattoos on the skin, the clothes are made of intertwined branches. I made some pencil sketch. I admit suggestions.
Oh the rendering on this is looking really nice! Be careful you don't lose your gesture in it though. I like the design so far too, the details are lovely
I'm glad you like it, I'll try to be careful with the gesture
Today's advances: I have defined more the earth girl's musculature. I still have many doubts about how I have to dress her. I have also drawn the lightning girl's weapon, since this light will affect me all around. I have made a small example of this light on the side of this girl's face.
Today's advances: While I decide on the earth girl's costumes I have advanced with the background. It is a simple perspective with two vanishing points. 
I have also included a ladder with several objectives: I think this ladder joins the eyes of the two girls and highlights the line of action. In addition, the two sections converge in the hands of the two girls, where there is tension in the scene.
I made the sketch and the idea of this scene the first few days, I enclose it in case anyone is interested
Today's advances: Today I could not work long: I have adjusted the background tones more, I have defined the hair of the lightning girl, and I have also drawn a hand of the earth girl.
Tomorrow will be day of drawing hands and feet: 3 hands and 3 feet. I will need patience.
Today I have not been able to draw almost anything, tomorrow I will advance and I add the progress for sure
Today's progress: I have made little progress, but I don't want to leave more than two days without showing you what I have done. I have defined the light of the beam on the girl. I have made the arm and hand behind the beam. I have refined the boots and feet of the same girl.
Is the naked girl going to be clothed? What's the story behind these two specifically?
@nesokaiyoh , The naked girl will be dressed. She will be from the earth faction. He will carry grass and earth covering his body and a medallion on his chest with the shape of his faction in green.
Attached speed sketch of how it will be clothed
Other tests I've done:
@nesokaiyoh The story behind the drawing is this, I have not put it even because my English is very bad and I want to be reviewed. It is that a virus is infecting many people in the world. This virus comes from a tree. The tree has evolved and needs human brains to survive and evolve. These infected people become ruthless killers who carry brains to the tree. Our heroine is the lightning girl, the only one who is able to disinfect people with her power.
Okay thank you for explaining to me! I would never have guessed any of that but it sounds awesome 
@nesokaiyoh It is true. It still does not seem so, luckily I have time until day 8 and it is not finished. I have not yet drawn a person lying behind dead and the Earth girl will have her hands covered in blood. I have told you my initial idea.
Latest advances:
I have drawn the victim of the earth girl has to retouch tones and colors and I have advanced defining more the whole drawing.
Tomorrow I will try to define some details that I am missing: The cape of the lightning girl, a gun of the earth girl on the ground stained with blood, the emblem of the earth girl, a tattoo of a tree on the chest of the earth girl ...
