The series was commissioned by Blake's friend John Linnell. The artwork is an unfinished pencil sketch painting because he passed away before he finished it. Blake worked on it from 1825 before he passed away in 1827. The painting is of two men, Dante and Virgil, climbing a mountain. The mountain path is a way for men to get to heaven and escape purgatory. In this painting, Virgil, who is in a blue robe, finds a steep route for them to get to heaven. They are both going up the rocky path which overlooks a cliff. The artwork is primarily in black and white with shaded areas. There is some colour on Virgil's robe and the sky. Dante is in the foreground of the picture with his back to the viewer. He is in a dark robe with his shadow on the rock to his right.

Virgil is higher on the path, facing Dante. The path is bordered by a water mass which is in dark pencil strokes. In the background behind Virgil is a partially covered sun by dark clouds. The sky is shaded a light blue, and its reflection is on the water body in the background. The artwork does not have much detail and colour apart from the shading used to create light and shadows. The lack of extensive detail shows its unfinished state compared to previous work that Blake had completed.

The spiritual world influenced Blake in his artwork. He depicts religious ideas and spiritual concepts in his painting. The Ascent of the Mountain of Purgatory work is influenced by Dante's poetry work, The Tyger. In the poem, which tackles death, the mountain was formed after Satan fell from heaven into the middle of the earth. In the poem, the story is told of when Manfred, an illegitimate son of Emperor Fredrick II, the Holy Roman empire king, was killed in the Battle of Benevento in 1266. Manfred repented for his sins before he died. He explains that prayer from the people on earth reduces the time he would spend in purgatory.

Dante and Virgil are thus looking for a way to escape purgatory and get to heaven. The picture shows them on the path to escape their purgatory. The Ascent of the Mountain of Purgatory is displayed in the Tate Gallery in London and is displayed with other paintings in the series Illustrations to Dante's Divine Comedy.