Throughout history, Monster Overlord appears in different types and shapes. Some have massive gigantic bodies; some could be as small as a halfling. This shape comes with its own disadvantages and advantages.
However, some Monster Overlords could change shape at their own will. From gigantic size to humanoid size and vice versa. This phenomenon is called monster transformation.
As for the trigger behind this phenomenon, nobody still found it. However, once a monster uses a transformation, they need a lot of time to get back to their previous form. Throughout history, people have classified monster transformations into two forms.
The first is a colossal form that appears to be a gigantic scale-sized monster. At this size, the monster is more oriented to large-scale destruction and has tougher defense along with its body size. However, they appear to be slower and easy to hit.