The novella being referred to here is Joseph Conrad's Heart of Darkness. The second narrator refers to the main character of Marlow who is telling his story to an anonymous narrator upon board a ship sailing up the Congo river. The character that is being referred to as having died is Kurtz and by the end of the novella it has been over a year since Kurtz has died. The mourning character refers to Kurtz's fiancee or Kurtz's intended. At the end of the story Marlow returns to Brussels and decides to visit Kurtz's fiancee, they have a brief encounter, she says she will mourn Kurtz forever, Marlow tells her that his last words were of her and then the story comes to an end.
Op art designs are usually geometric patterns used to create an illusion. Im not really sure what you mean by "how say two artists that drow these things"
