Question: The Sarantine Mosaicv alludes to works by which poet who helped to found the Abbey Theater?
Context: Schlierbach Abbey (German: "Stift Schlierbach" ) is a Cistercian monastery in Schlierbach, Austria founded in 1355, and rebuilt in the last quarter of the 17th century.  The original foundation was a convent for nuns, abandoned around 1556 during the Protestant Reformation.  The abbey was reoccupied as a monastery in 1620, and rebuilt in magnificent baroque style between 1672 and 1712.  The monastery again went into decline with the upheavals before, during and after the Napoleonic era.  It recovered only towards the end of the 19th century.  In the 20th century the abbey established a viable economy based on a glass works, school, cheese manufacturing and other enterprises.  The abbey is open to visitors, who may take tours, attend workshops and dine at the monastery restaurant. Vauluisant Abbey, near Courgenay in the canton of Brienon-sur-Armançon, Yonne, France, is a Cistercian abbey founded in 1127 by a group of monks from the abbey of Preuilly (Seine-et-Marne) who came to settle between the forest of Othe and the forest of Lancy, an area near the borders of Ile-de-France, Champagne and Burgundy that had come to be far from human habitation.  They diverted the waters of the little River Alain and by 1 April 1129, works were far enough advanced for Henri Sanglier, the archbishop of Sens, to consecrate the modest oratory.  By 1140 Vauluisant was fully operational.  The abbey church was consecrated in 1149.  In the second half of the 12th century, granges were established to cultivate abbey lands far from the abbey itself, at Beauvais, Toucheboeuf, Livanne, Cérilly, Armentières, worked by lay brothers who lived communally.  Ironworks were established, fuelled by the dense woodlands, and tileworks, whose kilns were also fired by forest timber.  The energetic Cistercians of Vauluisant produced more than the abbey needed; the surplus was sold in the market towns of Troyes and Provins, where the abbots retained domiciles, and at the cathedral town of Sens. Jad is a fictional solar god found in the works of Guy Gavriel Kay, including "The Sarantine Mosaic" series, "The Lions of Al-Rassan" and "The Last Light of the Sun".  In these books, all set in a fictional world loosely based on Europe during late antiquity and the early Middle Ages, Jad serves as an analog to God, as the focal point for an organized church (or group of churches) similar to the Roman Catholic and Eastern Orthodox churches.  In addition to the mainstream church of Jad, there are a number of heretical and schismatic movements alluded to or described.  The main division in the Jaddite faith stems from belief or disbelief in Heladikos, a fire-bearing celestial charioteer, and son of Jad.  Heladikos is the Jaddite analogue of Jesus.  Belief in Heladikos is outlawed as heretical by the time of Emperor Valerius II, an analogue of Justinian I.  This is a marked difference from actual Christianity, which is formed around faith in the son of God. Koulsy Lamko (born 1959) is a Chadian-born playwright, poet, novelist and university lecturer.  Born in Dadouar, Lamko left his country for Burkina Faso in 1979 due to the beginning of the civil war.  There, he became acquainted with Thomas Sankara and involved with the Institute of Black Peoples in Ouagadougou.  Lamko spent ten years promoting community theater in Burkina Faso through the Theater of the Community and helped found the International Festival of Theatre for Development.  Some of his poetry was published in "Revue Noire" in 1994.  In 1997 he co-released the album "Bir Ki Mbo" of mixed poetry and music in tribute to Sankara in collaboration with Stéphane Scott and Rémi Stengel.  A regular attendant at the Limousin Festival International des Francophonies, he briefly lived in Limoges, France.  He then moved to Rwanda, where he read for his doctorate at the National University in Butare while founding the university's Center for the Arts and the Theater and teaching theater and creative writing.  His doctoral thesis was on emerging theatrical aesthetics in Africa.  His experience in Rwanda led him to write his only novel, "La phalène des collines" (""The butterfly of the hills""), about the 1994 genocide. Gall Morel, O.S.B., was a poet, scholar, aesthete, and educationist, born at St. Gallen, Switzerland, on 24 March 1803; died at the Abbey of Einsiedeln on 16 December 1872.  His baptismal name was Benedict, but in the monastery he took the name of Gall.  In 1814, he entered the gymnasium at St. Gall.  A pilgrimage to Einsiedeln in 1817 influenced him deeply, and afterwards he entered the monastery school as a novice.  In 1820 he took the final vows, and after several years spent in theological and philosophical studies, was ordained priest in 1826, being appointed forthwith instructor in the monastery school.  From this period his life presents a picture of extraordinary activity.  From 1826 to 1832 he was professor of rhetoric, and until 1835 he lectured on philosophy.  In this latter year he became librarian of the abbey, and retained this office to the end of his life, while also fulfilling the offices of choral director (1835–40), prefect (1836), and rector (1848) of the abbey school, archivist of the abbey (1839–45), counsellor of education of the Canton Schwyz (1843–5), and subprior of the abbey (1846–52). Thomas Augustine "Gus" Martin (13 November 1935 – 16 October 1995) was an Irish academic, Anglo-Irish scholar, teacher, writer, broadcaster and literary critic.  During his career he was Professor of Anglo-Irish Literature at University College Dublin, Ireland; chairman of the Board of the Abbey theater Abbey Theatre (Dublin); and an elected member of the Seanad Éireann from 1973 to 1981. Kilcooley Abbey is a Cistercian abbey close to the village of Gortnahoe in Tipperary, Ireland.  The abbey is located within the grounds of the Kilcooley Estate.  This abbey dates from 1182 when Donal Mor O’Brien granted lands to the Cistercians, to build an abbey here.  The abbey which is a sister house to both Jerpoint Abbey and Holy Cross Abbey, is considered to be a hidden gem, tucked away in this remote corner of Co.  Tipperary.  The Abbey is found inside a private walled estate. William Butler Yeats ( ; 13 June 186528 January 1939) was an Irish poet and one of the foremost figures of 20th century literature.  A pillar of both the Irish and British literary establishments, he helped to found the Abbey Theatre, and in his later years served as an Irish Senator for two terms.  Yeats was a driving force behind the Irish Literary Revival along with Lady Gregory, Edward Martyn and others. Blinded by the Right: The Conscience of an Ex-Conservative is a 2002 book written by former conservative journalist David Brock detailing his departure from the conservative movement.  It is also the story of his coming out as a gay man.  In the book, he states that he visited gay bars with Matt Drudge and other conservatives.  The title alludes to the Bruce Springsteen song "Blinded by the Light", while the subtitle alludes to Barry Goldwater's "The Conscience of a Conservative", which helped define the modern conservative movement in the United States. The Sarantine Mosaic is a historical fantasy duology by Guy Gavriel Kay, comprising "Sailing to Sarantium" and "Lord of Emperors".  The titles of the novels allude to works by poet W. B. Yeats.
Answer: William Butler Yeats