The DX Thousand Ark Progrise Key is used by Kamen Rider Thouser in said special. To transform, the user presses the button of the Progrise Key to open it up, then the user sets it in the DX Ark Driver (sold separately) to transform into Kamen Rider Thousand Ark. The item on its own will play recorded lines coming from Gai Amatsu (played by Nachi Sakuragi) once you press the button.
Lastly, if you set the Dan Kuroto Progrise Key to the DX Hiden Zero-One Driver (sold separately), it will activate a unique sound. Pressing the button of the item on its own will play recorded lines coming from Kuroto Dan (played by Tetsuya Iwanaga) once you press the button. This Premium Bandai web exclusive set cost 7,150 yen and is set for an October release. Pre-orders will end on May 31st.