A Roman Empire TL created and written by Janus Antoninus (Red VS Blue on the Althistory Wiki). Starting from the reign of Marcus Aurelius, this TL divergences by contriving a replacement for Commodus, one that continues the until then successful line of adoptions that had sustained the imperial succession going back to Trajan.

In tackling such a common alternate history topic, I have striven only to write as good an example of that idea as I can manage. Like any alternate history, especially one with such an ancient PoD, I have treated this TL as more of an exploration than a hypothetical prediction: Rome could not have continued to prosper into its Sæculum Novum without being heavily transformed in both the short-run and the long-run, so I have found it fruitful to explore these possibilities and to develop one of them into a TL that at least feels realistic. I leave whether I have succeeded in these efforts up to the reader.

176 CE: Commodus dies of illness on an imperial tour of the eastern provinces
and Marcus Aurelius ends up adopting an orphan boy during his visit to Athens.

Following the pointless rebellion of Avidius Cassius, Marcus Aurelius and his family went on a tour of the eastern provinces that had, however briefly, supported the would-be usurper. Here Marcus faced tragedy after tragedy: first the death of his wife, Faustina, while in Cappadocia then the death of his last son, Commodus, over the Winter. Allowing himself little time to grieve, he continued onward with one of his daughters to Tarsos then, eventually, Alexandria, where he is said to have “conducted himself like a private citizen and a philosopher at all the schools and temples”. On his return to Rome, by way of Antioch then Athens, where he began by speaking at the Stoa Poikile on remaining steadfast in the face of death.

After speaking at the Stoa, Marcus Aurelius was approached by an orphan boy, not much younger than Commodus had been when he died. What passed between Marcus and the young Serenus, as he called himself, is not known but, whatever it was, Marcus did not leave Athens alone. Back in Rome, Marcus addressed the people, bemoaning his eight year absence, and offered them a congiarium and triumphus to celebrate his victories along the Danube. Before the celebrations, he spoke before the Senate of the death of Commodus and his adoption of Serenus, who he portrayed as a kindness offered to him by the gods during these dark times. That this blond boy bore an uncanny resemblance to a younger Commodus did not go unremarked by the literati of the time.

While Serenus was not granted imperium or other imperials powers in time for the triumphal celebrations, he was appointed Caesar after the address to the Senate and would not be far from Marcus for his entire stay in Rome. When news came that the situation on the Danube was deteriorating, Marcus set out to the frontier with his son in tow to finally bring this war to an end.