Worm: 'Ello.
Sarah: Did you say hello?
Worm: No, I said 'ello, but that's close enough.
Sarah: Give me the child. Through dangers untold and hardships unnumbered, I have fought my way here to the castle beyond the Goblin City to take back the child that you have stolen, for my will is as strong as yours, and my kingdom is as great. You have no power over me.
Jareth: I ask for so little. Just fear me, love me, do as I say and I will be your slave.
Sarah: I wish I did know what to say to make the goblins come and take you away.
Goblin: "I wish the goblins would come and take you away right now." That's not hard is it?
Jareth: So, the Labyrinth is a piece of cake, is it? Well, let's see how you deal with this little slice.
Sarah: Generous? What have you done that's generous?
Jareth: Everything! Everything that you wanted I have done. You asked that the child be taken; I took him. You cowered before me - I was frightening. I have reordered time. I have turned the world upside down and I have done it all for you! I am exhausted from living up to your expectations of me. Isn't that generous?
Hoggle: You have to understand my position. I'm a coward and Jareth scares me.
Sarah: What kind of position is that?
Hoggle: No position! That's my point.
Hoggle: And you wouldn't be so brave if you'd ever smelled the Bog of Eternal Stench. It's, it's...
Sarah: Is that all it does, is smell?
Hoggle: Oh, believe me, that's enough! But the worst thing is, if you so much as set a foot in the Bog of Stench, you'll smell bad for the rest of your life. It'll never wash off.
Sarah : You're horrible!
Hoggle: No I ain't! I'm Hoggle!
Answer: The necklace is a symbol of Jareth's power throughout the story. All the time that Sarah is in the Labyrinth, Jareth has more power than her, because she doesn't really know what she's doing, and isn't taking one particular path, just getting lucky at the right times. At the end, as we all know, Sarah triumphs, and Jareth's necklace changes to admit his defeat.