Hildegard of Bingen
The best-known writing of Hildegard of Bingen is a trilogy (1141–52) including Scivias, Liber Vitae Meritorum, (Book of the Life of Merits), and Liber Divinorum Operum (Book of the Divine Works). These include records of her visions -- many are apocalyptic -- and her explanations of scripture and salvation history. She also wrote plays, poetry, and music, and many of her hymns and song cycles are recorded today. She even wrote on medicine and nature -- and it's important to note that for Hildegard of Bingen, as for many in medieval times, theology, medicine, music, and similar topics were united, not separate spheres of knowledge.