And the life of the ebony clock went out with that of the last of the gay. And the flames of the tripods expired. And Darkness and Decay and the Red Death held illimitable dominion over all. (15)
Just like it began with death, the story ends with death. Death was spread everywhere at the beginning of the story, and now it really is: it has broken into the last fortress of life and destroyed it. Now death holds "illimitable" dominion. Put another way, death conquers all.