Read the following stanza from "The Raven."
But the Raven still beguiling my sad fancy into smiling,Straight I wheeled a cushioned seat in front of bird, and bust, and door;Then, upon the velvet sinking, I betook myself to linkingFancy unto fancy, thinking what this ominous bird of yore—What this grim, ungainly, ghastly, gaunt, and ominous bird of yore Meant in croaking, "Nevermore."
Which aspect of this stanza most clearly adds to the feeling of tension or dread in these lines?