The poem sketches a powerful official, a "commissioner," and sees him with a cold, unsparing eye. He looks like a hangman, and his face has already "entered into decay," as if death is working on him even while he holds office. The speaker mocks his tools of power: a "little pen" that seems tiny next to the "great chair," which is built for a kind of disease the poem hints at with the rhyme "disease, ease." Comfort and rot are tied together.
The last stanza shifts to an image from nature. The commissioner is there "to direct / another wren / toward the owls." A wren is small and vulnerable, and owls are predators, so the sense is that this man sends the weak toward danger with a signature or a signal. The speaker seems disgusted and sharply critical, though the tone stays dry rather than angry. The mood is chilly and ominous, with a bitter joke running underneath.