The Rainbow Bridge Machine (機械虹の橋を, Hashi Kumiwotsukuru Kikai?) is a quasi-magical machine in Final Fantasy Mystic Quest. Created by Otto and stationed in Windia on the second floor of his house, the machine can be used to create the Rainbow Bridge, a bridge to Pazuzu's Tower. However, when strong winds from Mount Gale damaged the machine, the Rainbow Bridge vanished. Once the winds had calmed, Otto repaired the machine and recreated the bridge, allowing Benjamin and Kaeli to enter Pazuzu's Tower.
The Rainbow Bridge likely refers to Bifröst, a rainbow bridge in Norse mythology that connected the realm of the gods, Asgard, with the realm of the mortals, Midgard.