バイド (BYDO) is a recurring antagonist force in the R-Type series.
At first, nothing was known about the enemies known as the Bydo Empire other than their name. In R-TYPE III, it was established that the Bydo were "the disastrous results of a gigantic composite biological weapon gone rogue, created by humankind in the 26th century". (It is now the 22nd century.) However, because they are united under the entity known as the Bydo Core, the term "Bydo Empire" continues to be used out of convenience.
This life-form has a multitude of different forms, due to their ability to convert any type of matter, living or not, into their own. Naturally, the craft the player pilots is no exception.
Sentient beings that have been transformed into Bydo are often unaware of the changes in their own bodies. This tragic plot is one of the most popular elements of the game series.