First Year: Before Stone Room
Right after Hermione leaves.
Harry turned to face the flames and then did something that would look like it came completely out of the blue to an observer. He brought both his hands down to his belt as if he was framing something seemingly causing a belt to appear. The belt was silver and had a large red gemstone and strange symbols all over it and was making a quiet, pulsing, stand-by noise. Dragging his left hand from across his body over the top of the casing and his right hand, with his index and middle fingers extended, through the air in front of him he let out a cry. He then placed both of his hands to the left side of the belt as if pushing a button followed by throwing the out to his sides.
Where Harry once stood there was now a armored figure reminiscent of a stag beetle. It had a black bodysuit on with red greaves, gold anklets and bracelets with red jewels, jeweled knee pads, red shoulder pauldrons, and red chest armor shaped like muscles with a gold collar. The armor had the same indecipherable writing as the belt on the chest armor and the collar. It wore a helmet with a silver mouthpiece styled like the mandibles of a bug, large red segmented eyes, and three golden horns with a red jewel in the center formed to make it look like a stag beetle.
This was Kamen Rider Kuuga: Mighty Form.
Kuuga then strode cautiously through the flames. On the other side was Professor Quirrel standing in front of the Mirror of Erised muttering to himself in a panicked fashion. Hearing a noise Quirrel turned around and brought his wand to bear. Seeing an unknown armored figure in front of him he did what most people did when caught doing something wrong. He panicked and shot a spell at the figure. Kuuga dodged and the spell took a large chunk out of the floor where he had been standing. Kuuga knowing that Mighty Form was not suited for taking enemies with a long reach in a relatively enclosed space did what came naturally. Returning to his transformation pose momentarily while keeping an eye on Quirrel, Kuuga called out for all to hear. Energy flared out of the belt and covered his body. KuugaI was once Lord VoldemortAnd in my rise to power I was reduced to mere shadow and vapor due to an unforeseen setback. I now seek a stone with which I will return greater than before! If you aid me I will see you ?t handle the stress yet. As he gets older he will be better.