The Fusionizer is a device capable of fusing dimensions. It was created by the Barian deity Don Thousand in the Yu-Gi-Oh! ZEXAL anime to fuse the Barian World and Human World using a million Barian Numbers stored within it. The device is not named in the Japanese version.
Don Thousand constructed this device and hid it in his palace. After his awakening, he showed it to Vector after guiding the Barian Emperor into the building. He explained that the device he can fuse the Barian World and Earth. This can be done once the level of hatred on Earth equals that of the Barian World. This process would assist in the destruction of the Astral World, as according to Don Thousand, it would boost his power to overwhelming levels.
However, the Barian Numbers stored within the device was not enough to accomplish this task, so Thousand was forced to anchor his host, Vector to the throne of his palace to focus their energies on creating more of them.
After the defeat of the first three members of the Fearsome Four of the Dark Dueling World, enough time had passed and many cards were manufactured. They used Mr. Heartland to spread the resulting Barian Numbers across Earth.
This machine was Don Thousand's ultimate machination to obtain the Numeron Code. By fusing the Human World and Barian World, the Numeron Code (which was on Earth, though he did not know its exact location) would become part of the Barian World. Don Thousand's powers as the deity of the Barian World, allowed him to obtain the Code's power, despite not knowing its location. In doing so, he was able to activate and wield the code's power without collecting all the "Numbers".