Private Tanner was a Sentinel who was part of the Search and Recovery team led by Lieutenant Nathan Hale and Captain Bo Richards that met Freedom First in Chicago, Illinois in an attempt to find former Secretary of War Henry Walker. He helped defend the rebel base from an attack by a Chimera raiding party.
When the Chimera sent in an Angel, Tanner fell to the ground due to the Angel's telepathically-projected mental blast, but he was able to resist it. He helped mowing down the last of the Hybrids as Hale finished off the Angel with a L210 LAARK.
He survived the battle, although it is unknown what happens to him afterward.