Black Doom



Black Doom is the cruel leader of the hive-minded Black Arms alien race, a species of parasites that travel from star system to star system in the Black Comet in search of alien populations to consume. Fifty years prior to the current war on Mobius against Dr. Eggman, Black Doom made contact with Professor Gerald, helping him to create Shadow the Hedgehog. Black Doom then revealed that he would return to Mobius fifty years later to claim it as his own, for which purpose Shadow was modified to stand against him and the Black Arms. Doom's return was delayed, however, by his species' conflict with the Xorda.

In the altered reality, Black Doom led the Black Arms to Mobius and was defeated by Shadow the Hedgehog. However, he created a new creature named Black Death to lead the species after his demise.

Assisting Professor Gerald
When Professor Gerald was trying to complete his Ultimate Lifeform project to cure his granddaughter Maria Robotnik's Neuro-Immuno Deficiency Syndrome, he found barriers to his research he could not overcome without outside help. Making a deal with Black Doom, he extracted some of Doom's blood to help him finish the process. The result was Shadow the Hedgehog, the Ultimate Lifeform with the abilities granted by Gerald's process and also with a measure of Doom's own power, granting Shadow his Chaos Control abilities. Black Doom afterwards departed, vowing that he would make his return fifty years later, prompting Gerald to modify Shadow so that when the time came Mobius would have him for a protector. (StH: #171)

Delay in Return
The Black Arms were making their way back to Mobius in order to feast upon the inhabitants when they ran afoul of the Xorda, another alien race which had its sights set on the planet. Refusing to allow an impending feast be denied to him, Black Doom entered his people into an interstellar war with the Xorda, which has devastated the Bem homeworld of Argentium and many other planets and star systems. (StH: #170, CSE)

New World
After Sonic reset his world back to normal, the entire Zone changed. In this new universe the Black Arms had already been defeated by Shadow. The Black Comet was not destroyed however, and Doom's replacement, Black Death, led the Black Arms to Mobius again for a second invasion. (SU: #59; SSSM: #9)