Umbriel, a dusky, melancholy sprite, / As ever sully'd the fair face of light, / Down to the central earth, his proper scene, / Repair'd to search the gloomy Cave of Spleen.

At the beginning of Canto 4, we are introduced to the gnome Umbriel. Gnomes are the spirits of women who were prudes in their lifetime, and accordingly Umbriel’s role is to turn Belinda against men while also making her behavior annoying to men. As part of this job, Umbriel journeys to the Cave of Spleen, or melancholy, to make Belinda even more upset than she already is. Just as Ariel is associated with air, Umbriel is associated with earth, here carrying the connotation of shadows, gloom, and heaviness.

But Umbriel, hateful Gnome! forbears not so; / He breaks the Vial whence the sorrows flow.

This quotation appears in Canto 4, just after the Baron’s oath to wear the lock forever. That Umbriel uses a vial of tears from the Cave of Spleen to enhance Belinda’s distress emphasizes the way the gnomes and sylphs of the poem serve to control Belinda’s actions instead of her own agency. Belinda’s outburst in this framework comes not from her rational thought but supernatural manipulation.

Triumphant Umbriel on a sconce's height / Clapp'd his glad wings, and sate to view the fight: / Propp'd on the bodkin spears, the Sprites survey / The growing combat, or assist the fray.

This last appearance of Umbriel occurs in Canto 5, just before the Court gathering descends into a chaotic fight. He is satisfied that not only will his manipulation turn Belinda against men, but her sobs and fighting will be considered uncouth. Notably, Umbriel is not alone, as other sprites watch and intervene in the battle at will. Umbriel fulfills a role in the poem not unlike the gods in Greek and Roman epic who intervene on behalf of their favorite mortals. He is part of the techniques Pope uses to create a mock epic.