His most important works are outstanding examples of distinctively coloured late Baroque painting, some of which make use of tenebrism while others have a lighter atmosphere. Although Raab was a highly skilled landscape artist, religious figural scenes predominate in his output. Raab was very familiar with late Venetian school of art and the composition of idyllic landscapes with atmospheric light effects. The painting The Fourteen Holy Helpers depicts a group of saints (Achatius, Barbara, Blaise, Catherine of Alexandria, Christopher, Cyriacus, Denis, Erasmus, Eustachius, George, Giles, Margaret of Antioch, Pantaleone, Vitus), revered by the Catholic church. Their intercessions were believed to assist the healing of various ailments. The tradition dates back to the 14th century in the Rhineland as a result of the epidemic later known as the Black Death. The Ostrava canvas is example of Raab’s mastery. The richly figural and spatially segmented composition displays all the elements of Raab’s style without any other input.