From the Manual of the Game:
Marcus is a man of the people, and the settlers worship him because he contributes greatly to their welfare. Nothing is dearer to his heart than the protection of all those under his command. As he comes from the ranks of the settlers, he is familiar with their customs and traditions.
Passive skill: Recruiting Swordsmen and Bowmen costs less gold
Active skill: Marcus can distribute torches to troops near him so that they can get new ammunition for attacking buildings.