Answer
Upon Caracalla's passing, Macrinus swiftly took the reins of power, assuming the illustrious title of Augustus. This honorific, derived from the esteemed ancient Roman emperor Augustus, symbolized Macrinus' claim to imperial authority and sought to legitimize his ascension to the throne. By adopting this venerated title, Macrinus aimed to establish himself as the new leader and unify the Roman Empire under his rule.