Complex sentence: Despite the victory of Elagabalus over Macrinus, he still had to defeat the usurpers who had risen in opposition to him, among them were Seius Carus, Castinus, Verus, and Gellius Maximus.
Split into simpler sentences: Despite the victory of Elagabalus over Macrinus, he still had to defeat the usurpers who had risen in opposition to him. Among these are Seius Carus, Castinus, Verus, and Gellius Maximus.