In 1775 Francesc Santacruz was already working on the ornamentation of the dome of the Chapel of Saint Benedict and he created the medallions that would be painted by Pasqual Savall and continued after his death by Josep Laiga. The gilding was entrusted to Pere Pau Vinyals, considered the best master of that period. The altarpiece strictly speaking was not commissioned until 1688 and it seems that it was paid for by the Erill family, owners of the Torre Negra.
The architectonic structure of this baroque altarpiece is made up of three streets, two floors upon the predella and the upper attic. The resulting panels contain six oil canvases, dedicated to the reformers of the Benedictine order (Saints William, Joan Gualbert, Silvestre, Romuald, Robert and Pere Celestí).
In the main space of the altarpiece there is a niche that houses a sculpture of Saint Benedict that is too small, given that the original disappeared in 1936.
The vertical separation elements are volumetric figures of angels bearing candles on the lower part and musicians on the upper part. Above their heads are the coats of arms of military orders that follow the Benedictine rule.
There is a false tradition according to which the altarpiece was paid for by King Felipe II, in 1585, and a historical reason would explain this confusion: the aim of linking the chapel with the monarchy, so that in the intrados of the entrance arcade there are the portraits of the monarchs of the House of Austria who reigned before 1700 (Charles I, John of Austria, Philip II, Philip III and Philip IV). On the reveals their two-headed eagles are also painted holding and protecting the oval coat of arms of the Monastery.
The war interrupted the work and in 1734 Pere Ruiz and the painter Joan Grau were commissioned to complete it.
The dynastic change meant that in the reign of Philip V two lions were added above the exterior cornice, the symbol of the House of Bourbon, in identical protective attitude towards the Monastery. The tympanum contains a fresco painting of the passing of Saint Benedict, underneath which there is a big coat of arms of the Monastery.