Create Mordor like Scene

Step 1. Open our photo. Copy background Layer (Ctrl + J) and name new Layer "mordor".

Step 2. Go to Layers palette and click on Create new adjustment Layer.

Select Solid color and use this color #de8c17.

Select Blending mode of that Layer to be Color Burn.

This change should be applied only to the sky and not to the ground. So we have now to mask ground. Pick Gradient tool, select Black,White as gradient, click on mask and make gradient so that it mask the ground. Mask should look like this

Step 3. Once again click on Create new adjustment Layer. Select Curves and make diagram look something like this.

This step has the purpose to make some contrast in the sky. Now we have to copy the gradient mask we made in previous step. Simply press and hold Alt, then click and drag gradient mask to blank mask of our new Layer.

Step 4. Now we have to make new adjustment Layer. Click on Create new adjustment Layer. Select Color Balance and set the values as I did.

Set Blending mode of this adjustment Layer to Darken. Once again we have to copy Gradient mask to this Layer.

Step 5. Merge all visible Layers to another Layer. You'll do this by pressing Alt + Ctrl + Shift + E on keyboard. Name new Layer "mordor like".

Step 6. Copy Layer "mordor like" (Ctrl + J). Go to the Image - Adjustment - Replace color. Select that portion of the sky near the mountains and with plus tool add selection until you get it approximately as on the picture below.

Select Blending mode for this Layer to be Lighten.

Step 7. Finally we have to make this swamp a little bit darker. Merge all visible Layers by pressing Alt + Ctrl + Shift + E. Name this Layer "final". Go to the Create Adjustment Layer, select Curves, and make the diagram looks like mine.

Now copy the gradient mask from any of the adjustment Layers below to mask on this Layer. After copying make sure to invert this mask by pressing Ctrl + I. Change opacity to 65% and we are finished.
Final image looks like this

See you!