For the tutorial level, I created a small and simple collection of rocks that could be duplicated, scaled and rotated to build variation. Due to how the fog-of-war system reveals tiles, the rocks had to be packed neatly into squares.
Now for the puny Earthlings...
Starting from a provided low poly base, I created the high poly and final low poly models. Almost all of the characters were handled this way. The textures were created in Substance Painter.