Influencing and manipulation are essential pivotal actions in this novel. Using Lord Henry as the chief manipulator, Wilde makes Dorian Gray the pawn of the elder man's game.
The purpose of using influence and manipulation is simple: Lord Henry aims to make Dorian into an experiment where combines the glorious beauty of a young man with the lowest end of sinning for the sake of a so-called "new Hedonism" that precludes for the seeking of sensations, and for the living of life for the sake of pleasures.
Although Lord Henry has a variety of friends, including Basil Hallward, he does not get to influence them the way that he achieves to do so with Dorian. In fact, he influences and manipulates Dorian so much that he teaches Dorian how to manipulate others.
One of the key moments in the novel where manipulation is touched upon is after the death of Basil Hallward. Dorian wanted to get rid of the body and his first thought was to call upon one of his former friends; one of whom he had influenced so badly that, like many others, had stopped speaking to Dorian. We know that, after his friend, Alan Campbell, refused to help Dorian, the latter
..stretched out his hand, took a piece of paper, wrote something on it...and pushed it across the table..Campbell ..felt as if his heart was beating itself to death in some empty hollow.Dorian turned round and came and stood behind him, putting his hand upon his shoulder."I am so sorry for you, Alan," he murmured, "but you leave me no alternative.
While we do not know what the paper said, we know that it must have been bad enough to warrant Campbell's obedience. Campbell commits suicide shortly after this event.
This event could have been prevented if Dorian had listened to Basil when the latter warned him about Lord Henry's tendency to manipulate and badly influence others. Yet, Dorian never listened. The conclusion is that Lord Henry is supposed to represent sin
that it was through certain words of his, musical words said with musical utterance, that Dorian Gray's soul had turned to this white girl and bowed in worship before her. To a large extent the lad was his own creation. He had made him premature.
Lord Henry's "musical voice", the venom of the message that he spread, and the natural weakness of Dorian's psyche all contribute that Dorian becomes completely manipulated by Harry and, eventually, Dorian will manipulate others as well.