Complex sentence: At the same time, Areobindus himself had secret contacts with another Berber leader, Cutzinas, who led the Numidian Berbers, and who had promised to murder Antalas once battle was joined, a plan that Guntharic revealed to Antalas.
Split into simpler sentences: At the same time, Areobindus himself had secret contacts with another Berber leader, Cutzinas, leader of the Numidian Berbers. Cutzinas had promised to murder Antalas once battle was joined, but Guntharic revealed this plan to Antalas.