Complex sentence: Much of the information on his career comes from people hostile to him, for example, Gerald of Wales, who wrote favorably of the Welsh prince Rhys ap Gruffydd, Giraldus Cambrensis "Itinerary" p.113 called Longchamp that "monster with many heads".
Split into simpler sentences: Much of the information on his career comes from people hostile to him. For example, Gerald of Wales, who wrote favorably of the Welsh prince Rhys ap Gruffydd, Giraldus Cambrensis "Itinerary" p.113 called Longchamp that "monster with many heads".