The New World held the premise of a fresh start, a seemingly untouched continent and an escape from the corrupt ways of the Old World. The colonists were free to build their Puritanical society without the threat of Catholicism, having believed evil to be left behind on the shores of England. Of course, The New World had its own mysterious evils to discover, such as the forces of nature, the unexplored wilderness and the natives lurking within. As such an ambiguous subject, evil was a prominent theme within American Literature, challenging religious theology, questioning morality and establishing the existence of the subtle evils hidden away in the human mind. While there are a large number of American texts exploring the theme of evil, from slavery to witch trails, I'll be focusing mainly on the Dark Romantic authors, Poe and Hawthorne, and how evil manifests through mentality, guilt and religious ideologies. I will also be discussing the allegorical role of evil and its impact on the reader's interpretation of the text.
To begin, I'd like to give a brief introduction on Dark Romanticism, and how it's defined as a genre. In his essay, Thingdings 1974 ,Thompson, describes Dark Romanticism as 'the fallen man's inability to comprehend haunting reminders of another supernatural realm that yet seemed not to exist,' he goes onto explain that 'seemingly perverse or evil moral choices' were merely the product of a 'nameless guilt' and the suspicion of 'delusion' towards the mind's perspective of the 'external world.' He claims the genre focuses mainly on the psychological aspects of the human mind, the differences between the external and internal struggle, and how evil is symbolised through the embodiment of supernatural images of 'Satan, ghosts and ghouls.' The genre also acts as an 'opposition' to the transcendentalist writers of the time; nature is seen as something dark, foreboding, a mysterious force, in which evil takes form.
Quote: Thompson (1974: 5)
Applying this to 'The Raven,' in which nature takes an allegorical role, Poe establishes a strong sense of evil through his descriptions of the world outside the scholar's chamber. 'Midnight dreary' and 'bleak December' symbolise the end of a day and a year, foreshadowing the narrator's later descent into madness. These descriptions also suggest the presence of the supernatural; 'the hour of witching.' 
When the narrator investigates the 'tapping' and 'peers' into the 'darkness' outside, he becomes both fearful and caught up in the mysterious landscape. The symbol of the Raven itself also represents an evil side of nature; the narrator refers to it as a "grim, ungainly, ghastly, gaunt, thing of evil' from 'plutonium shores.' In referencing Pluto, the God of the Underworld, the raven is given a diabolical appearance, bringing the question of the narrator's soul into consideration. Ravens are strongly associated with death, spirits and darkness, and Poe even claims in his essay, 'The Philosophy of Composition,' that he intended the bird to be a sign of 'ill omen,' bringing in the theme of death and hopelessness. The narrator also describes a more diabolical nature to The Raven and its "fiery eyes" burning into his "bosom's core." This is most noticeable towards the end of the poem, where the narrator's soul is left 'floating' in the 'shadow' of the Raven, as if the bird has driven the narrator to such despair that he relinquishes his soul.
If we look at the themes of nature and evil in a more psychological sense, considering the narrator's state of mind, the loss of Lenore and how he isolates himself within his chamber, the symbols of both take on a different meaning. In his essay, Poe describes the poem as one that explores the suppressed human want for "self-torture," which is shown through narrator's apparent grief; he is 'weak and weary' and purposely isolates himself from the rest of society. It is only by opening the window, the narrator allows nature to intrude inside the safety of his chamber walls. Poe believed man was born with the 'need to do evil,' and explained this idea through 'perversity,' a desire to act 'for the reason that he should not.' This suggests the narrator is perhaps harbouring an inner-evil, an unresolved conflict which presents itself in, as Edward H. Davidson describes in his critical study of Poe, in 'amorphous shapes of death.' (pp. 113, 1980)
Poe claims he purposely chose the theme of death, as it was 'the most melancholy' subject in the 'universal understanding of mankind.' He goes onto explain 'death allied with the Beauty,' in this case the death of Lenore, 'a beautiful woman' is
unquestionably the most poetical topic in the world.' The narrator's melancholy over the loss of Lenore suggests his perception of the external world may not be entirely reliable. His clouded judgement allows his imagination to conceive 'dreams no mortal ever dared to dream before' and 'fantastic terrors.' Again, referring back to Davidson's essay, 'Death, Eros and Horror,' we can see that the 'objects of horror' he is tormented by are not themselves 'necessarily horrible;' they are manifestations of 'the mind,' which identifies them and can eventually be 'destroyed by them.' (pp.125, 1980)
If we consider the horrors of the poem are simply symbols of a maddened mind, can we assume this was Poe's way of dramatising the 'perverse' inner conflict the narrator was experiencing? His want to remember his lost lover, to bring her back through the persistent questioning of the raven, despite already knowing 'its only stock and store. It is, as mentioned before, as if he 'delights in self-torture,' deriving some kind of 'frenzied pleasure' from the repeated process of despair. Poe claims the Raven gains an 'emblematical meaning' here, of 'Mournful and Never-ending Remembrance,' leading the reader onto the assumption that maybe the narrator has become lost in his memories, trapped inside his mind, a chamber filled with memories of his lover. He is fearful and curious of the nightmarish landscape outside, unaware of the potential evil that lurks inside his mind.
Poe's use of evil and the diabolical is deceptive; the reader's experience echoes the narrator's; we are distracted by the supernatural imagery, caught up in the seemingly 'demonic and fiendish' appearance of the Raven along with his feelings of alienation and grief. As the narrator persists in his futile questioning 'life, death and moral judgement lose their reason for being,' (Davidson, pp.124), and we're left with nothing more than a trapped soul and feathered embodiment of evil. This provides, as SOMEBODY states,' a means of intruding between the reader and the idea. Society's views on morality were constantly changing, while 'guilt and evil become all the more appalling' (Davidson, pp.205) due to their 'existence in the ever worsening condition of the world.' While Poe's narrator sets the blame of his loss and suffering upon the raven; 'take thy beak from out my heart,' the reader is left to wonder otherwise, the questioning arising whether all men become capable of evil after isolated themselves within guilt and grief.
Bearing in mind these concepts of guilt, blame and isolation, I'll now be moving onto Hawthorne's 'Scarlet Lettter,' discussing how he allegorises evil and sin though his characters. With Hawthorne's Puritanical background in mind, it is important to consider his outlook on his ancestor's religious beliefs. In the novel's introductory chapter 'The Custom House,' which is believed to be an autobiographical piece; (its narrator shares many similarities with Hawthorne), the narrator speaks of discovering the manuscript with the faded letter 'A,' whilst also expressing his resentment towards the strict Puritan rules and values. He comments on the oppression of his desire to write, claiming his ancestors would scorn him for not 'being serviceable to mankind in his day' or 'glorifying God' (pp. 1385) This acts as a powerful literary device, constructing a framework in which Hawthorne can explain his purpose for writing 'The Scarlet Letter,' establishing themes such as isolation; the speaker feels alienated from his 'sluggish' workers and that there are 'few who will understand him,' and also the struggle between the individual and society, through his personification of the American eagle above the Custom House entrance -- a symbol of freedom yet a 'threat to mischief.' He also establishes a base, inviting the reader to distinguish between the 'good and evil traits' of the Puritans.
Within the Scarlet Letter, Hawthorne's characters symbolise and embody many different perceptions of evil, in effect bringing the Puritan values into question and exemplifying man's capacity to become evil. If we consider the character of Pearl, the child who 'represents the sins of both Hester and Dimmesdale, (Martin 108)' She is a personification of the scarlet letter, a symbol of sin. The narrator and village people refer to her as mischievous and demonic -- 'an elf child,' and even Hester, at one point, questions the origin of her child: 'O Father in Heaven -- if Thou art still my Father -- what is this being which I have brought into the world?'
The narrator also associates Pearl with nature,  bringing the relationship of Puritans and natural world into discussion. The Puritans associated nature with evil: that 'wild, heathen Nature, of the forest, never subjugated by human law, nor illumined by higher truth' (293) This may be in reference to the Original Sin, in the Garden of Eden, indicating Satan was at work within the wilderness. It also points to the fact society has no power or control over the wilderness, therefore it is something to be feared. As Pearl has been rejected from Puritanical society along with her mother, she forms a bond with nature and is liberated. During chapter sixteen, Pearl and Hester meet Arthur Dimmesdale in the forest, and whilst the woods are described as being 'great black' and a place of all 'the guilt and trouble of the world,' it is in these woods where Pearl feels most at ease; she 'adorns herself with flowers' and communicates with the brook, attempting comfort it. Through this bond with nature she becomes a symbol evil, rejecting society and embracing nature. However, Hawthorne also shows an alternative side of nature through Pearl's relationship to the forest, as it becomes 'the playmate of a lonely infant,' (pp. 1462) symbolising that the forest is not an entirely evil force and criticising the narrow-mindedness of Puritanical views on nature. This provides a new insight into the society which uses religious ideology not only to serve God but to also preserve functionality and manipulate the population within.
Another character who engages with nature is Roger Chillingworth, who uses the natural remedies from the forest in his manipulation of Dimmesdale. As a doctor, he is a man of science rather than spirituality, using his knowledge to torture others instead of theological means, which adheres to the Puritanical belief of scientists.  As a character, Chillingworth's symbolism is quite difficult to define; 'Hawthorne remains faithful to his penchant for ambiguity, he has his narrator insistently demonize Chillingworth." (John L. Idol, Jr) We're told Chillingworth has transformed into Satan quite blatantly, adapting his 'physician's ecstasy from Satan's.' (1:138) Chillingworth's vengeful intentions are 'blacker than any sin,' Dimmesdale asserts, suggesting the corruption of the human heart is the very worst sin. In his haunting torture of Dimmesdale, Chillingworth takes the role as antagonist, though towards the end of the novel Dimmesdale recognises him as a punishment from God, a way of suffering for his sin. This brings into consideration Chillingworth's true motive; he blames Hester for his sinning, claiming 'by thy first step awry, thou didst plant the germ of evil, but, since that moment, it has all been a dark necessity." (1:173)
The notion of a 'dark necessity' almost echoes the narrator's behaviour in 'The Raven;' his darkened perception of the world, after the hurt and loneliness he's suffered. Chillingworth claims Hester's sin produces his own sin, raising the question of whether all humans have the potential for evil or if the grief of another's sin can lead to into an diabolical descent.
To conclude, Poe and Hawthorne illustrate the fact evil isn't always something visible, something to escape from, or put a name or image to. As dark romantic writers they believed that all humans were capable of evil, that it was a 'perverse urge' or the product of extensive suffering and loneliness. They demonstrate that the perception of evil and sin are continually changing, taking on new mysterious forms, though the only constant recognisable evil is built into the human soul, awaiting a trigger.