Sibling Different was a survivor of the Last Great Time War who worked with Sibling Same to create a Paradox TARDIS. (PROSE: The Paradox Moon) She wore several different types of masks.
History
Same and Different were active during the Last Great Time War, although they couldn't remember what they had done during this time. The Thirteenth Doctor speculated that they might have been part of a fraction of Faction Paradox who remained in the universe during the Time War. When the War ended, this part of the Siblings' history was trapped behind the time lock. (PROSE: The Paradox Moon)
During the Kotturuh Crisis, two Faction Paradox masks ended up on the doorstep of the Verbier Museum of the Impossible alongside other paradoxical items which had fallen through reality due to the temporal chaos. The proximity of the masks to these other items allowed the masks' owners, (PROSE: Canaries) Different and Same, to be reanimated as ghost-like beings driven by paradox energy. (PROSE: Canaries, The Paradox Moon)
Finding themselves in the time after the Time War, Different and Same hired a troupe of Autons to replace the actors at the production of The Saga of the Time Lords at the Masque Magestrix, turning the play into a trap for any remaining Time Lords. When the Tenth Doctor took Rose Tyler to the show, Rose noticed Different in the audience. The Doctor and Rose managed to stop the Autons from fulfilling the Siblings' orders. (PROSE: He's Behind You)
To learn more about the Doctor, Different and Same visited the Stormcage Containment Facility and interrogated Henrik Chyll. (PROSE: Visiting Hours)