Republic mod armor was a type of modular armor issued to Galactic Republic soldiers during both the Mandalorian Wars and the Jedi Civil War. The armor was designed to be easily upgradeable to afford great protection, including resistance to mind-affecting powers from Force users, even as the armor began to age.
While trying to escape Taris and find Bastila Shan, the mind-wiped former Jedi Revan found and took a set of this armor that once belonged to Elam Mattic in a password-rigged chest.