Mago was born in 239-240 BC and arrived in Spain, the center of Barcid power, at the age of thirteen. It is likely that he accompanied Hannibal in his early Spanish campaigns between 221-219 BC, before setting off with his brother for the invasion of Italy in 218 BC. Mago took part in Hannibal's early victories at the Ticinus, Victumulae, Trebia, Lake Trasimene and Cannae.
Mago was given an important task by his brother at Trebia, and during the night before the battle, he set out with 1,000 handpicked infantry and 1,000 cavalry with the task to conceal himself within a watercourse between the two camps which had steep banks overgrown with brambles. Polybius tells us it was a perfect place for an ambush: the place was admirably adapted for putting them off their guard; because the Romans were always suspicious of woods, from the fact of the Celts invariably choosing such places for their ambuscades, but felt no fear at all of places that were level and without trees...(3.71)
Mago successfully concealed his force during the night and awaited the time to strike. The next day Hannibal successfully lured the Roman army from it's camp with his Numidian cavalry, who feigned a retreat drawing out the Romans across a cold river (and without breakfast) to the ground of Hannibal's choosing. The Roman army, led by T. Sempronius Longus, consisted of 16-18,000 Roman infantry, 20,000 allied Latin infantry, 4,000 cavalry, and a contingent of Celts from the Cenomani. As the armies lined up and the infantry lines closed and locked in combat, Mago attacked. His timing was perfect, and the charge into the rear of the Roman lines threw the whole Roman army into confusion (Polybius, 3.74). By the end of the battle, most of the Roman army had been destroyed, save some 10,000 Romans who had managed to cut through Hannibal's lines and fled towards Placentia.
At the famed battle of Cannae, Mago stood shoulder-to-shoulder with Hannibal near the front lines of the Carthaginian center while commanding the Celtic and Spanish infantry, drawing them back in an organized and planned retreat thus encouraging the Romans into a trap.
After the victory over the Romans at Cannae, Hannibal sent Mago to Carthage, where he made quite an impression when he poured out hundreds of golden rings at the entrance of the Carthaginian Senate building that had been taken from the bodies of the Romans killed in action.
Mago later commanded all Carthaginian forces in Spain and lead a third invasion of Italy (this time by sea) in 205 BC. Wounded in a battle in Cisalpine Gaul, he was recalled back to Carthage along with Hannibal to aid in its defense. Before arriving, however, he died at sea.