Bryn Magus was the commander of the battlestar Galactica, father of Iphigenia and Paulus, and foster-father to Lt. William Adama. Some time prior to the Cylon War (as depicted in the game), Adama's father often saved Magus' life; when Adama was orphaned, Magus welcomed him onboard Galactica.
After the sneak attack at the start of the War, Magus and other Colonials spent a year in a Cylon prison camp before being liberated by the battlestar Perseus.
Note
The "Battlestar Galactica" video game has its own continuity as a result of its association with the failed Original Series continuation revival in 2001.
In some write-ups of the game, his name is written as "Magnus" (Latin for "great"). However, the write-ups are in error, as in the game he is clearly named Magus.