I think that the poppet with the needle inside of it represents the level of cruelty and malevolence that Abigail possesses. It is reflective of the play's theme that those in the position of power might not possess the will of the people in mind. Abigail's meteoric rise to power is one in which she becomes the center of political order and political control. The fact that someone with so much power would go through such an intricate and cruel approach to ensure that her "enemy" is eliminated is scary. It is this theme that the play seeks to bring out in that the realm of politics can be an awfully cruel one if there are not institutional checks and controls to limit a devious individual from wrestling control of the system. In Salem's case, Abigail is able to manipulate the town's fears and, in the process, she is able to seize this instant of emotional contagion for her own control and her own sense of hold over the town. In doing so, she is able to remove an enemy in Elizabeth and use political control for her own gain in coveting John Proctor. In this, the political manipulation of the populace is evident, critical to a thematic understanding of the play.