During the Great Galactic War, the Sith Lord Darth Vich formed a personal army comprised of Rattataki warriors. During the war, Vich attempted to use his army to stage a coup against the Sith Empire's ruling Dark Council but ultimately failed. The surviving Rattataki were either killed or enslaved.
Sources[]
Rattataki on The Old Republic Holonet (content now obsolete; backup link)