In the world of Earth-9997, the original Victor Von Doom is long dead, having perished in an explosion at the Baxter Building years prior to the series start. However, a figure wearing the iconic iron mask and green cloak still haunts the wasteland.
In a shocking twist, it is revealed that the man behind the mask is actually Reed Richards. After failing to stop the Terrigen Mists and losing his family, Reed donned the armor of his greatest rival as an act of ultimate penance. By becoming "Doom," Reed forced himself to live in a shell of cold iron, attempting to solve the world's problems through the calculated logic of a dictator because his life as a hero had failed.
This version of Doom represents the tragic theme of Earth X: that even the greatest minds can be broken by the weight of a world they could not save.