Chaplains serve a much different role in Legions than they do in the Chapters of the 41st Millenium. Each had a unique tradition, in harmony with the philosophy of their Primarch. For the Blood Angels, the Chaplaincy were wardens, secret watchmen to a gene curse ill-understood. To the Word Bearers, they were heralds, inspired orators driving back the darkness of Old Night with enlightened Imperial doctrine.
For the Ultramarines, their service took on a form of front-line heroism. Driving the line forward, they embodied the very finest traditions of the Ultramarines.
This Chaplain wields one of the fabled Blades of Perdition, a gift from a champion of the IXth during the scouring of Ultramar. There are a few details like this spread across this commission – the shared heritage of the loyal against the traitor.