|This article is about a/an source of power in Kamen Rider Build.|
The Nebula Gas (ネビュラガス Nebyura Gasu) is a type of gas from the crack of the Sky Wall.
Faust is able to change people into monsters by injecting a concentrated formula of the Gas in liquid form into a test subject or using Fullbottles of their own for their agents. After the contaminant elements in the gas are purified by Misora Isurugi, the gas becomes a vital component of the creation of Build's Fullbottles. It's later learned that the gas can be further condensed into a gel for the creation of Sclashjellies.
Nebula Gas can cause the Bugster Virus to mutate into the Nebula Bugster. These Nebula Bugsters serve as the fuel for Kaisei Mogami’s inventions, namely the Enigma and the Kaiser system and its Nebulasteam Gun. Nebula Gas on its own is a powerful fuel source, as Takumi Katsuragi designed the derivative Transteam Gun to run off of it.
Nebula Gas can be neutralized by Build Genius Form.
Nebula Gas is a byproduct of the Sky Wall, as it contains compounds not found on Earth.
When Killbas arrived in the new world and reactivated the Pandora Box by using Ryuga Banjo as a catalyst on the white Pandora Panel, those who were experimented on with Nebula Gas in the original world had their former memories restored.