I suspect that Charles Dickens invented Orlick because he intended to use him in a future installment to attempt to murder Pip's sister. This would lead to Biddy's coming to live and work as housekeeper and nurse in the Gargary household, and it would eventually lead to Joe marrying Biddy when Mrs. Joe finally died as a result of the injuries inflicted by Orlick. The assailant remains a mystery for a long time. Then in Chapter 53, when he has lured Pip to an isolated rendezvous and is preparing to kill him, Orlick reveals the truth.
“I come upon her from behind, as I come upon you to-night. I giv' it her! I left her for dead, and if there had been a lime-kiln as nigh her as there is now nigh you, she shouldn't have come to life again."
Apparently Mrs. Joe never knew the identity of the man who had nearly killed her, since she had been attacked from behind. She was unable to speak for the remainder of her life, so she could not provide any information that would have been useful in deducing the killer's identity. Orlick was naturally suspected, but he seemed to have an alibi. He has no qualms about telling Pip how he nearly killed Pip's sister, since he expects his helpless victim to be dead in a matter of minutes.
Great Expectations was published in serial form in Charles Dickens's weekly periodical All the Year Round between December 1, 1860 and August 1861. Dickens was writing the novel as it was being published, and he probably did not know exactly how he would finally expose Orlick as the man who had nearly killed Joe's wife. But Dickens was a genius, and he undoubtedly knew that he would come up with some good scenes when the appropriate time arrived. In the meantime he could let his readers wait and wonder. It was questions such as this that kept Dickens's readers on both side of the Atlantic waiting breathlessly for the next installment.
Orlick plays a very important role in "Great Expectations" by Dickens.
Dickens presents Orlick as a foil to Pip. Orlick is first introduced in ch.15. as an assistant to Joe who has hired him as "a journeyman at weekly wages." Orlick is always jealous of Pip's privileged status as Joe's adopted son although he is supposed to be regarded only as an apprentice while working in the forge. This results in a lot of resentment and Orlick often quarrels with Joe over this issue. This jealousy and resentment has dangerous repercussions and proves almost fatal for Pip in ch.53 when Orlick almost manages to kill him.
It is then that the readers realise how much of bitterness and resentment Orlick has harboured against Pip:
"you was favoured, and he was bullied and beat. Old Orlick bullied and beat eh? Now you pays for it. You done it; now you pays for it."
It is also then that Orlick confesses that it was he who Killed Mrs.Joe because he couldn't stand her terrible temper, and that it was he who had been trailing Magwitch from the time he returned from Australia.
In ch.29 Pip meets Orlick as the watchman at Miss Havisham's house. We learn that Orlick had left the forge soon after Pip came to London and became a watchman at Miss Havisham's house. He lives in a small poorly ventilated room near the gate of Miss Havisham's house. He has been appointed as the watchman of the house because of the convicts who were escaping from the prison ships. This chance meeting serves only to increase Orlick's hatred for Pip who appears at Miss Havisham dressed smartly as a gentleman.