Black Doom/Pre-SGW

Black Doom was 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.

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 devastated the Bem homeworld of Argentium and many other planets and star systems. (StH: #170, CSE)

Background information

 * Black Doom was the main villain of the 2005 video game Shadow the Hedgehog, where it was revealed that Shadow was made from his DNA, making him Shadow's biological father. This was confirmed to be canon in the Archieverse in The Complete Sonic Comic Encyclopedia.
 * Due to issues with SEGA, Ian Flynn previously stated that Black Doom and the Black Arms will not be making a proper appearance until they are given the green-light to have them defeat the Xorda and come to Mobius. (1)