[The following bits contain spoilers, so you might want to skip out on it if you want to go into the game fresh without knowing much ahead of time.]
In Valkyria Revolution, Maxim appears in front of Amleth and others as a rival character. He was the second prince of Ipseria, a nation that was conquered by the Ruzhein (Rus) Empire. The DLC will explain why he’s serving under Claudius Powlovich Kiev, the emperor that took over his home country.
The DLC will make Maxim a playable character, and the DLC, titled “Side Story: Ragnite-Bodied Soldier, The Name Is” and it will be fully-voiced and available for you to play after beating the main story. Afterwards, you’ll get to go through all the missions with Maxim on your side.
Maxim is a “Scout” type unit, and is able to use wind and fire magic. He’s also able to use his exclusive “Dual Handguns” side arms as well.
Valkyria Revolution is available in Japan for PlayStation 4 and PS Vita. The game is headed Westward in Q2 2017 for PlayStation 4, PlayStation Vita, and Xbox One.