Wikipedia
Gannys was a Roman general and eunuch who commanded the troops of Elagabalus against Emperor Macrinus in the Battle of Antioch.
According to Edward Gibbon in his Decline and Fall of the Roman Empire:
"... Antoninus himself, who in the rest of his life never acted like a man, in this important crisis of his fate approved himself a hero, mounted his horse, and, at the head of his rallied troops, charged sword in hand among the thickest enemies; whilst the eunuch Gannys, whose occupation had been confined to female cares and the soft luxury of Asia, displayed the talents of an able and experienced general." (I, vi)
According to Dio Cassius:
"1. Because of his slaying at Nicomedeia at the very outset of his reign Gannys, the man who had brought about the uprising, who had taken him to the camp, who had also caused the soldiers to revolt, who had given him the victory over Macrinus, and who had been his foster-father and guardian, he was regarded as the most impious of men. 2 To be sure, Gannys was living rather luxuriously and was fond of accepting bribes, but for all that he did no one any harm and bestowed many benefits upon many people. Most of all, he showed great zeal for the emperor and was thoroughly satisfactory to Maesa and Soaemis, to the former because he had been reared by her, and to the latter because he was virtually her husband. 3 But it was not at all because of this that the emperor put him out of the way, inasmuch as he had wished to give him a marriage contract and appoint him Caesar; it was rather because he was forced by Gannys to live temperately and prudently. And he himself was the first to give Gannys a mortal blow with his own hand, since no one of the soldiers had to take the lead in murdering him."