Private Kaffen Groll is a Tanker with the nickname "Knuckles".
Groll is attached to Downfall Company, coming under Stroun Coren's One-Four Charlie fireteam along with his friend and comrade Qillen Bel-Jenta.
Given that Downfall was deployed to the surface during the Second Liberation of Mibes, it is reasonable to assume that Groll was one of the Tankers encountered there by Elm Caden and his team. The same can be said of Operation Keystone, which visited the surface of Guathelia, and the mission to the Viskr homeworld (→LOTD, TRD).
Groll would also have been present during the investigation at Forge Ruinous, when MAGA and Tanker assets were deployed to the surface of Lopama in order to discover the whereabouts of a missing Tanker platoon. He would have taken part in Operation Sabre on the surface of Palanda Ire, and acted as a member of the strike team sent to the surface during the Siege of Damastion (→FSS).