Step 10: Draw the enderman's eyes as tiny rectangles inside the head. Use the construction lines as guides for the placement and size of the eyes. The outer sides of the eyes should touch the sides of the head. There should be a small gap between the eyes. Draw two tiny lines in the middle of each eye for the pupils.
Step 11: Use the long diagonal line on the left as a guide to draw the enderman's arm. Follow the path of that guide as you make the arm thicker. The shape of the arms is basically a really long and thin rectangle. Sketch the shape of the arm lightly at first as you follow the path of the guide. When you get the shape of the arm right, darken the lines. Use a ruler if you need it. Add another long line along the middle of the arm to make it blockier. Or you can just use the guide line for this.
Step 12: Use the initial cube as a guide to draw the block the enderman is holding. Follow the shape of the guide as you darken the lines but don't overlap the lines for the arm on the left.
Step 13: Darken the rectangle under the head to create the enderman's body. Add a vertical line on the left to make it blockier.
Step 14: Use the diagonal line on the right as a guide to draw the enderman's other arm. Widen the shape of the arm by adding a parallel line on either side of the guide.