Heathcliff's role as an avenger is helped by his intelligence and understanding, not just of his own motivations, but of the motivations of others. He recognises the source of Isabella's infatuation that-: "she abandoned this under a delusion" - "picturing in me a hero of romance". He also capitalises on Linton's poor health by inviting the pity of Cathy so that her affection and sympathy would facilitate a marriage that would leave he, Heathcliff, as master of the Grange.
As Heathcliff seeks his revenge, he becomes fiendish and is constantly associated with diabolical feelings, images and actions. The use of the imagery reinforces the inhuman aspect of Heathcliff. He regrets saving the infant Hareton. Nelly recalled that his face bore the greatest pain at he being the instrument that thwarted his own revenge. He takes perverse pleasure in the fact that Hareton was born with a sensitive nature which Heathcliff has corrupted and degraded. Heathcliff's pleasure at this corruption is increased by the fact that-: "Hareton is damnably fond of me". Heathcliff's cruelty is also evident when he hangs Isabella's dog despite her protestations. His attitude is devoid of fatherly feeling. He sees him only as a pawn in his revenge and his main consideration lies in calculating whether Linton lives long enough to have married Catherine so having acquired Thrushcross Grange-: "We calculate it will scarcely last 'till it's eighteen." Once the marriage has taken place, Linton's life is seen as worthless by Heathcliff-: "His life is not worth a farthing, and I won't spend a farthing on him" His cruel treatment of Isabella is, for him, a source of enjoyment. He tells Nelly-: "The more the worms writhe, the more I yearn to crush the entrails" Isabella recognises the sadistic treatment by Heathcliff and asks- "Is Mr. Heathcliff a man - is he the devil?"
There is, however, another side of the novels leading character. At no point in the novel can we doubt Heathcliff's eternal faithfulness to Catherine. His love survives her rejection of him-: "It would degrade me to marry Mr. Heathcliff" and despite her marriage to Edgar, Heathcliff's love for her continues undaunted. Heathcliff suffers much emotional rejection, but at no point does he waiver in his loyalty to her-: "I seek no revenge on you...the tyrant grinds down his slaves and they don't turn against him, they crush those beneath them" His genuine concern for Catherine prevents him from exacting direct revenge from Edgar. He says to Catherine-: "I would of died by witches before I would have touched a single hair of his head." When hearing of Catherine's illness, he exclaims-: "Existence after loosing her would be hell" In this statement, we can see the extent of Heathcliff's dedication and loyalty to Catherine and the sense of desolation her death would bring to him.
At times in the novel, Heathcliff is portrayed as a tormented spirit. After the death of Catherine, Heathcliff's lust for love is gone. His existence is then focused totally on exacting revenge. As his death approaches, he confesses to Nelly the extent of Catherine's hold over him, though she's now been dead 18 years-: "I cannot look down into the floor, her features are shaped in the flags...in every cloud, in every tree." The degree in which Heathcliff is tormented by Catherine is reflected when he said-: "Why did you betray your own heart, Cathy?...you love me, what right had you to leave me?" The sense of despair following news of Catherine's death is a good example of Heathcliff's tormented spirit-: "I cannot live without my life, I cannot live without my soul" He, said Nelly, howled not like a man, but like a savage beast getting goaded to death with knives and spears. Life for Heathcliff after Catherine's death is an unnatural existence. He feels he belongs with her both in body and in spirit and has already arranged with the Sexton to be buried beside her. Life for him is "like bending back a stiff spring". The young Cathy recognises that Heathcliff has rejected all society although she doesn't realise that his attachment remains to her late mother-: "Mr. Heathcliff, you have nobody to love you...your cruelty arises from your greater misery."
From the beginning of the novel and most likely from the beginning of his life, he has suffered pain and rejection. When he is brought to Wuthering Heights by Mr. Earnshaw, he is viewed as a thing rather than a child. Mrs. Earnshaw was ready to fling it out of doors, while Nelly put it on the landing of the stairs hoping that it would be gone the next day. Without having done anything to deserve rejection, Heathcliff is made to feel like an outsider, following the death of Mr. Earnshaw, suffers cruel mistreatment at the hands of Hindley. In these formative years, he is deprived of love, sociability and education, according to Nelly, Hindley's treatment of Heathcliff was "enough to make a fiend of a saint". He is separated from the family, reduced to the status of a servant, forced to become a farm hand, undergoes regular beatings and is forcibly separated from Catherine. Personality that Heathcliff develops in his adult life has been formed in response to the deprivation of his childhood. Heathcliff received constant reminder of his lesser status e.g. on his first visit to the Grange, Catherine is taken into the Linton household, whereas Heathcliff is rejected, made fun of, and alienated. Later, when Catherine returns to Wuthering Heights, her changed appearance further alienates Heathcliff, a point emphasised during the visits of the Linton children, Heathcliff was not considered fit to join the party. The final sense of alienation and the most damning occurs with Catherine's marriage to Edgar, this he considers a betrayal of his love for her, in favour of the social status and civilised existence of the Grange. Heathcliff is however proud and determined and does not cower when confronted by those who consider themselves to be superiors, his determination was evident when taking advantage of Mr. Earnshaw's favouritism and exchanging horses with young Hindley, though his situation and position is somewhat worsened after the death of Mr. Earnshaw, Heathcliff's pride nevertheless remains intact. When Catherine returned to the Heights after her five week stay at the Grange, she is much changed in appearance and makes fun of the ragged Heathcliff, when ordered to shake hands with Catherine by Hindley, Heathcliff refuses, saying-: "I shall not stand to be laughed at, I shall not hear it". Similarly, when insulted by Edgar during one of his visits to the Heights, Heathcliff empties a toureen of applesauce over him. Finally, when the realisation dawns on him that Catherine has chosen status, wealth and position in preference to him, he disappears for three years and returns in the guise of a gentleman.
Part of Heathcliff's survival mechanism during the period that he is being terrorised by Hindley, is the thought and prospect of revenge, he is determined to have is own back and confesses to Nelly-: "I don't care how long I wait, if I can only do it at last, I hope he will not die before I do".
As Heathcliff approaches death and a reunion of Catherine, his resolve for revenge weakens until he no longer has an interest in that former preoccupation-: "I have lost the faculty of enjoying their destruction". This dousing of the flames of Heathcliff's revenge is a catalyst not just in the novel but in the histories of the Earnshaw and Linton families. Hareton and Cathy are spared, the sense of evil visited upon them by Heathcliff is removed and there occurs a spiritual renaissance within Wuthering Heights.
Heathcliff is a many faced character, in his early years he is characterised somewhat by his fiery temper, his sulleness, his proud nature, his fierce attachment to Catherine, his spitefulness and his capacity for hatred. The adult Heathcliff, who returns to Wuthering Heights after a three year absence, is a super-human villain driven by revenge, distorted by the sense of the wrongs done to him and made emotionally unstable by Catherine's marriage. This later Heathcliff is characterised by callousness by an incapacity to love and eventually by an all consuming passion for revenge against those who have wronged him and for unification with his beloved Catherine.
