Camulus (or Camulos) was a theonym for a God of war of the Celts that the Romans identified with Mars (a close equivalent of Greek Ares) by interpretatio romana.
Camulus was a significant God of war of early Great Britain and Gaulish people, most specifically among the Belgae (the Remi Tribe) located around modern day Rheims.
The wild boar was known to be his symbol. This God of war wielded an invincible sword. Some coins found in Camulodunum revealed this God of war with what appeared to be ram-horns.
Here is one of the better analyses available about Camulus. YouTube Video
In Roman mythology, Camulus was closely associated with Mars. Mars was identified by the Romans with Ares due to the blending between Greek and Roman cultures. Mars was considered the protector/guardian God of Rome and referenced in ancient mythology as the father of Romulus and Remus.
It was believed by some that the Romans descended from Mars. As the Roman Empire expanded, Mars was equated with Celtic Gods of war such as Camulus.
Mars slightly differed to his Greek counterpart Ares. To the Romans, Mars was a heroic God; while Ares was often depicted as savage, cowardly, unpredictable and held in much less esteem. Mars was often depicted as a warlike God of protection. Ares was one of the 12 Olympians in Ancient Greek mythology.