Complex sentence: The Antae sent Kelagast with his brother, Mezamir as an envoy to the Avar Khagan Bayan I to negotiate the release of Antae prisoners, the envoy was however slain (among some historians because of Mezamir's arrogance).
Split into simpler sentences: The Antae sent Kelagast with his brother Mezamir as an envoy to the Avar Khagan Bayan I to negotiate the release of Antae prisoners. The envoy was however slain (among some historians because of Mezamir's arrogance).