Short answers, pulled from the story.
Otto of Freising (c. 1111-1158) was a German bishop and Cistercian monk who served as bishop of Freising from 1138. He was the fifth son of Leopold III, margrave of Austria, and was closely related to Conrad III of Germany and Emperor Frederick Barbarossa. He is best known for two major historical chronicles written in the twelfth century.
Otto of Freising wrote two major works. The first is the Chronica sive Historia de duabus civitatibus, an eight-book philosophical and historical treatise written during the German Civil War of 1143-1145. The second is the Gesta Friderici imperatoris, a chronicle of Emperor Frederick I commissioned by Frederick Barbarossa himself.
The Chronica of Otto of Freising contains the first documented reference to Prester John. Otto recounts a meeting with Bishop Hugh of Jabala, who described a Nestorian Christian king in the East from whom Crusader states hoped to receive aid. This single passage launched a legend that spread across medieval Europe for centuries.
Otto took part in the Second Crusade in 1147. The section of the crusading army he led was decimated, but he reached Jerusalem and returned to Bavaria in 1148 or 1149.
Otto framed history as a sequence of four world empires ending with Rome, after which power passed to the Byzantines, the Franks, and the Germans. He counted Frederick I as the 94th emperor since Augustus. He argued that Pope Gregory VII's excommunication of Henry IV in 1075 ushered in the seventh and final age of history, a period of crisis preceding the Antichrist.
Otto of Freising died at the Cistercian monastery of Morimond in Burgundy on the 22nd of September 1158, wearing the habit of a Cistercian monk. A statue in his honor was erected at Freising, Bavaria, in 1857.