In just three short lines, the poem sketches a woman and the life around her. The first two lines describe her "extravagant collection of antiquities," which suggests someone with money, taste, and a love of rare old things. Then the last line drops the punch: she is "married to a bastard." The dash before it works like a sudden turn, as if the speaker has been admiring the display and then lets slip what they really think.
The contrast is what makes the poem sting. Her beautiful, carefully gathered objects sit beside a husband who is anything but refined. The speaker seems to feel a mix of pity and dry disapproval. There may also be a hint that the collection is a kind of consolation, something lovely she can control while her marriage is not. That is an inference, since the poem never says it outright. The mood is quiet, wry, and a little sad, with a blunt word landing hard after a polished opening.