The Mutant Conversion Machine was a device created and utilized by Magneto for the Brotherhood of Mutants. It transformed the biochemical structure of non-mutant humans, giving them mutant abilities. However, the mutations were short-lived, as it broke down the cellular structure of affected individuals, ultimately killing them in the process.
The conversion machine was first built by Magneto on Genosha. It was designed to induce artificial mutations within non-mutant humans. Specifically, he intended to use the machine to convert the various world leaders and dignitaries at the upcoming World Summit Meeting on Ellis Island, so as to have them identify more with mutant-kind. The conversion machine would be installed within the torch of the Statue of Liberty so that it would have maximum effect.
The machine was operated by Magneto's own mutant power - producing a mutation-inducing radiation field. However, a great deal of energy was required on his part to make the machine operate, even within a limited range. He could not operate it to the desired range he wanted without killing himself in the process. Fortunately, Magneto somehow discovered the existence of Rogue and her ability of power absorption. He now planned to utilize her power so that he would be able to survive the machine's process.
As Rogue was running away from home, Magneto sent Sabretooth to track and capture her. Sabretooth failed in the capture, as the X-Men intervened to save both Rogue and Logan. Senator Kelly, an anti-mutant activist in the U.S. Senate, was abducted by the Brotherhood and was used as the first test subject for the machine. It proved successful on Kelly, giving him a liquid-oriented mutation. With the help of his new mutation, the senator was able to escape from Genosha. When Mystique, disguised as Bobby Drake, encouraged Rogue to leave the X-Mansion, the Brotherhood was ultimately successful in capturing her at Salem Center's train station. Following Rogue's capture, Kelly found his way to the X-Mansion and asked for medical assistance. Through this, it was discovered that Kelly's mutation was very unstable, causing his cellular structure to destablize. This ultimately led to his death.
As the X-Men attempt to stop Magneto on Liberty Island, they have an opportunity to warn him of the instability of his machine. However, he arrogantly refuses to listen, convinced that the machine will convert the humans rather than kill them. After an intense battle with Sabretooth, the X-Men are able to subdue Magneto and destroy the machine before its energy field reaches Ellis Island.