Apollinaris Sidonius or Saint Sidonius Apollinaris (circa 430 –489) was a poet, diplomat, and bishop, becoming one of the few authors from 5th century Gaul whose works survived. He was one of 4 Gallo-Roman aristocrats whose letters survived in quantity during the time period, making him an invaluable primary source on the Goths.
Theodoric, of course, was the King of the Visigoths from 418 to 451. Theodoric's forces contributed decisively to the victory of the Romans against the Huns in 451, but he himself was killed during the battle of Châlons. Jordanes records two different accounts of his death: one was that Theodoric was thrown from his horse and trampled to death; the second was that Theodoric was slain by the spear of the Ostrogoth Andag, who was the father of Jordanes's patron Gunthigis.