Richter

Richter is a leader of a powerful faction within The Front. The impression is given by the dialogue that Richter coordinates most of the Front's daily military operations while Macil acts as more of a visible leader.

 Spoiler warning : plot or ending details follow 

After Macil is revealed to be possessed by a Spectre, and subsequently destroyed by the player, Richter assumes Macil's role as commander of The Front. This will happen in both plot branches once the player has killed The Bishop, whether or not Macil or The Oracle is the next target. In the "good" plot branch (in which The Oracle is killed first), Richter has a much larger role, as he coordinates military assaults against The Order in order to both harass their ability to wage war and give the player more time to accomplish his mission.

Richter is the only NPC in the game to only be talked about - you never actually interact with him, as he is presumed to be always in the field both before and after Macil dies.