Commodus (161-92 CE) is perhaps best remembered now as the Emperor in Gladiator (2000); the real life Commodus was certainly fond of fighting as a gladiator, though he was also co-emperor with his father, Marcus Aurelius, and ruled for several years after he died, which is something the film happily ignores. (It also ignores most of the rules of gladiatorial combat, but that’s a separate issue.) The unreliable and over the top Historia Augusta gives a scurrilous story to explain Commodus’ mania for gladiators and claims that Commodus’ real father was a gladiator.
19 1 Some say, and it seems plausible, that Commodus Antoninus, his son and successor, was not his child, but the product of an affair; 2 they embroider this assertion, moreover, with a story current among the people. On a certain occasion, it was said, Faustina, the daughter of Pius and wife of Marcus, saw some gladiators pass by and burned with love for one of them. Later, when she had been sick for a long time, she confessed the passion to her husband. 3 And when Marcus reported this to the Chaldeans, it was their advice that Faustina should bathe in his blood and thus couch with her husband. 4 When this was done, the passion was ended, but their son Commodus was born a gladiator, not really a prince; 5 for afterwards as emperor he fought almost a thousand gladiatorial bouts before the people, as shall be related in his life. 6 This story is considered plausible, as a matter of fact, because the son of so virtuous an emperor had habits worse than any trainer of gladiators, any actor, any fighter in the arena, anything brought into existence from the dregs of all dishonour and crime. 7 Many writers, however, state that Commodus was really the child of adultery, since it is generally known that Faustina, while at Caieta, used to choose out lovers from among the sailors and gladiators. 8 When Marcus Antoninus was told about this so he might divorce, if not kill her, he is reported to have said “If we send our wife away, we must also return her dowry”. 9 And what was her dowry? The Empire, which, after he had been adopted at the wish of Hadrian, he had inherited from his father-in‑law Pius.
Historia Augusta 19
The historian Cassius Dio, who was a senator under Commodus, gives an eye witness account of some of Commodus’ activities in the arena:
He killed a hundred bears all by himself, shooting down at them from the railing of the balustrade – the whole amphitheatre had been divided up by means of two intersecting cross-walls which supported the gallery that ran its entire length so the beasts, divided into four herds, might more easily be speared at short range from any point. In the middle of the struggle he became weary, and taking from a woman some chilled sweet wine in a cup shaped like a club, he drank it at one gulp. At this both the people and we senators all immediately shouted out the words so familiar at drinking-bouts, “Long life to you!” And let no one feel that I am sullying the dignity of history by recording such events. On most accounts, to be sure, I should not have mentioned this exhibition; but since it was given by the emperor himself, and since I was present myself and took part in everything seen, heard and spoken, I have thought proper to suppress none of the details, but to hand them down, trivial as they are, just like any event of the greatest weight and importance. And, indeed, all the other events that took place in my lifetime I shall describe with more exactness and detail than earlier occurrences, for the reason that I was present when they happened and know no one else, among those who have any ability at writing a worthy record of events, who has so accurate a knowledge of them as I.
19 On the first day, then, the events that I have described took place. On the other days he descended to the arena from his place above and cut down all the domestic animals that approached him and some also that were led up to him or were brought before him in nets. He also killed a tiger, a hippopotamus, and an elephant. Having performed these exploits, he would retire, but later, after lunch, would fight as a gladiator. He fought as and dressed in the armour of the secutores, as they were called: he held the shield in his right hand and the wooden sword in his left, and indeed took great pride in the fact that he was left-handed. His antagonist would be some athlete or perhaps a gladiator armed with a wand; sometimes it was a man that he himself had challenged, sometimes one chosen by the people, for in this as well as in other matters he put himself on an equal footing with the other gladiators, except for the fact that they enter the games for a very small sum, whereas Commodus received a million sesterces from the gladiatorial fund each day. Standing beside him as he fought were Aemilius Laetus, the prefect, and Eclectus, his cubicularius; and when he had finished his sparring match (and, naturally, won it) he would then, just as he was, kiss these companions through his helmet. After this the regular contestants would fight. The first day he personally paired all the combatants down in the arena, where he appeared with all the trappings of Mercury, including a gilded wand, and took his place on a gilded platform; and we regarded his doing this as an omen. Later he would ascend to his customary place and from there view the remainder of the spectacle with us. After that the contests no longer resembled child’s play, but were so serious that great numbers of men were killed. Indeed, on one occasion, when some of the victors hesitated to kill the defeated, he fastened the various contestants together and ordered them all to fight at once. Then the men who were bound fought man against man, and some killed even those who did not belong to their group at all, since the numbers and the limited space had brought them together.
Cassius Dio, Roman History 19-20. (The complete Roman History can be found here.)