"You've got those kids thinking you're some kind of holy vampire." - Max, to Marrow
While most transgenics where built to be the ultimate soldiers; Marrow (Manticore designation unknown) was created to be a human blood bank, or has he puts it "the red cross" for transgenic combat teams. Marrow, and others like him are the backbone of the combat medic units that follow transgenic soldiers into battle. In addition to their normal training, they have extensive training in anatomy/physiology, combat medicine and emergency battlefield surgery, making them a one-man medical corp. Manticore designed all transgenics to be universal donors but in Marrow's case they decided to go further and create a being with perfect blood. His blood contains higher levels of hemoglobin, which carry oxygen to body tissues, high levels of platelets and fibrin to speed clotting of wounds and elevated levels of pain-killing endorphins and adrenaline. His body also has a higher production rate than the average human or transgenic and a higher-than-average blood pressure required for quick transfusions.
The blood of these transgenics was designed for the use of other injured or incapacitated units, but consumption of the blood by normal humans has been seen and leads to enhanced physical capabilities like increased strength, speed and resistance to pain. The endorphin and other "feel-good" neurochemicals present in the blood also make the blood very addictive.
Because of his appearance Marrow can not entirely pass for human and may be mistaken for an an anomaly. His genetic makeup has given him a rather pale complexion, ice blue eyes and most disturbingly large protruding veins stretching all over his body.