X-Antibody

When the Digital World becomes so overpopulated the super computer (Yggdrasil) that governs the Digital World can't handle it anymore. His solution? Wipe out the vast majority of the Digimon with the X Virus, he chooses a very small percentage to be moved to a new Digital World cause he plans to destroy the old Digital World. Those who were not chosen but survived anyway and moved to the new world had a rare gift known as the X-Antibody, this anitbody when activated changed their appearance and made them more powerful.

Those who have the X-Antibody are generally disguished by the X in their name and sometimes an X placed on their body somewhere. There are few with the X-Antibody that isn't distinguished by an X after their name but this is because there is no version of them in existence that doesn't have the X-Antibody so there is no need to distinguish the normal and X-Antibody apart with the X surname.