While his main backers were magnates of Austrasia, the Byzantine support consisted of treasure to buy followers and it is probable that Gundovald spent time in Constantinople before setting off to conquer parts of Gaul.
According to Gregory of Tours, he was educated with great care and wore his hair long in the style of the Frankish kings, At some point, his mother presented him to Childebert I claiming that his father, Chlothar I, hated him.
Regardless, upon his return to Gaul, he was received in Marseilles by Bishop Theodore and subsequently he set off to join Duke Mummolus at Avignon.
However, Gundovald was soon forced to flee to an island in the Mediterranean after Guntram Boso arrested Bishop Theodore for introducing a foreigner to Gaul.
Accompanied by the Duke and also another called Desiderius, Gundovald soon set off to the district of Limoges, where he was raised up as king on a shield at the tomb of Saint Martin.
Gundovald also asked for an oath of allegiance to Childebert II, his supposed nephew, in all the territories that had previously belonged to Sigibert I.
Next, he marched on Toulouse and sent messengers to its Bishop Magnulf, but the inhabitants of the city prepared to resist the supposed pretender.
After the discussions with the Bishop went wrong, Magnulf was prodded with spears, punched, kicked, tied up with rope and banished from his own city Gundovald then moved on from Toulouse and was pursued by an army made up of the inhabitants of Tours and Poitevins.
Guntram stretched the messengers, until they admitted that Gundovald had been asked to accept kingship by Childebert II's leaders.
With Guntram's army approaching, Gundovald soon crossed the Garonne and made for Comminges or Convenae in the foothills of the Pyrenees.
When he arrived in Comminges, Gundovald claimed that he had been invited by all those who dwell in Childebert II's realm and ordered the inhabitants to bring food and supplies inside the wall.
They made reference to his nickname ballomer, his painting skills and the cutting of his hair by Chlothar I and Sigibert I. Gundovald went on the ramparts and answered back to the attackers.
The constructed siege machines mainly consisted of battering rams, with the aim of knocking down holes in the walls.
The next day the gates of the town were opened and Guntram's men slaughtered all the common people, while all the buildings, including churches, were put to the flame and destroyed.