The figure below looks pretty "rough" as a concept drawing. But it is ok for you to be not good at drawing concept art. You can go to the Clicli Editor to select the models you need.
All the models in Clicli Editor are divided into two different styles: Cartoon and Realistic. In order to ensure a consistent style in your scene, you can choose Realistic models to build the environment. (Rocks are picked from realistic models.)
Usually, stylized models only keep a few core details on texture, because they have restrictions on total polycount. But realistic models have more large, medium, small, and micro surface details on texture.
Sometimes you can't find the most suitable model directly from CliCli Editor. So, you need to arrange and combine the existing models to create a better result you want.
For example, you can put different break wall parts in a certain way to achieve the shape of ruins.
Or you can stack them to make a broken tower.
Do not limit your ideas. Be brave to try new combinations, which may lead you to some unexpected results.
Here is the last step before you went to edit your terrain, the camera setting. You need to enable Real-Time Update to help you check the changes in the camera. And set Field of View from 30 to 75, which provides you with a wilder view.
Set the boss in front of the cave and the tower ruins on the hill. You can control the light angle to move your shadow direction by changing the Time setting.
After figuring out the most props you need, you can start to build some big map information for your environment. Topography tool is usually used to sculpt the landscape, and different mountain trends can be obtained by rotating the angle of the same Rock. In theory, you can use only one stone to cover the whole scene.
Then you just need to build other mountain shapes in the same way.
If you want to attract people’s attention to the Boss and the Cave behind it, you can set all the stone directions to aim at the middle scene.
After finishing building the mountain rocks, you still need other medium or small details to enrich the scene. At the same time, you also need to make sure that the props you set can also make the audience focus on the center of the picture.
You can use Vegetation Tool to paint some grass on the map. Do not forget to make sure that the color of the grass matches the geographical features. Next, you can put some stones around the path to create a more mountain vibe.
At the current stage, you have finished most of the natural elements in the picture. Then you need to add the ruins into this environment. In order to make the scene look more old and damaged, you can modify most of the building angles. At the same time, you can use a few dead trees and broken parts to make the picture more storytelling.
In the function of Art Style, you can try and switch different filters, adjust the in-game time in the upper right corner of the interface, and create a dark atmosphere.
If you are interested, you can also try Lighting and Fog effects to make the picture more unified.