Complex sentence: Little does he know how that billboard will go on to change his life, the image begins to haunt him with a threshold, and hallucinations in which she portrayed appears as a tempter and Dr. Antonio as a St. George with his spear the dragon.
Split into simpler sentences: Little does he know how that billboard will go on to change his life. The image begins to haunt him with hallucinations in which she appears as a temptress and Dr. Antonio as St. George, to spear the dragon.