Based on the description provided, the artist most likely used:
organic shape
Organic shapes are those that are not regular or symmetrical and can include shapes inspired by living organisms. Since we are talking about a creation of a cotton candy creature, the artist likely used organic shapes to represent the fluffy, irregular forms of cotton candy and potentially to give the creature a more lifelike appearance. Texture could also be an element to emphasize the fluffy nature of cotton candy, but without more information about whether texture was heavily utilized in the drawing, organic shape is the more likely primary element used for the concept of a cotton candy monster.