Complex sentence: Kaloyan also wanted revenge against the Byzantines for emperor Samuel's 14,000 blinded soldiers, and called himself "Romanoktonos" (Roman-slayer) as Basil II was called "Bulgaroktonos" (Bulgar-slayer).
Split into simpler sentences: Kaloyan also wanted revenge against the Byzantines for emperor Samuel's blinding of 14,000 blinded soldiers. Kaloyan called himself "Romanoktonos" (Roman-slayer) after Basil II, who was called "Bulgaroktonos" (Bulgar-slayer).