"The Rime of the Ancient Mariner" has a great deal to do with the character of the mariner. The poem doesn't tell us how old the mariner is when he kills the albatross, but certainly he is a much younger man than he is at the opening of the poem when he stops the wedding guest to tell the guest his story. It was the mariner's character that led him to kill the albatross for no reason. He was a man who did not appreciate nature. In Part IV, the mariner refers to what he sees in the ocean as "slimy things" and he sees the ocean as the "rotting sea". He has been unable to pray since he killed the albatross and his crewmates flung the carcass around the mariner's neck. Toward the end of this part, the mariner again refers to the water-snakes but this time, they are simply that and no longer "slimy". As soon as he is able to pray, in the last stanza of Part IV, the albatross falls from his neck and he sees beauty in all the nature around him. It is this realization that nature is beautiful and that all living things deserve respect that changes the mariner's character. He still must pay for his sin of killing the albatross though, and that is what he is doing when he stops someone to tell him his story. The retelling is his penance. This is his character now in his old age. He is certain and relentless in his retelling to whomever he stops.