He belonged to one of Asturias's most renowned families, and is likely the same "Bernaldo de Quiros" thought to have lived in Lena.
El caballu is a romance of 330 verses which takes the form of letters.
The author praises the qualities of a horse that the narrator wants to sell in Oviedo/Uviéu to carry the banner of the city.
The tone of the poem features elements of parody and irony.
This, along with other features such as exaggerated images, make it a typical example of the Baroque style, according to Professor Ramos Corrada.