Highests do not have a natural shape. They are semi-transparent core energy of a certain color (Pink-red for Exetior) flying in the air, and slightly distorting the perception of light inside themselves. The older Highests gets, the more light energy they accumulates, which transforming them into a different form, which creates the illusion of a "body". When the "body building" is completed, Highest becomes less transparent, turning into the color that core-energy had.