“Dobby!” she screamed, and even Bellatrix froze. “You! You dropped the chandelier — ?”

The tiny elf trotted into the room, his shaking finger pointing at his old mistress.

“You must not hurt Harry Potter,” he squeaked.

“Kill him, Cissy!” shrieked Bellatrix, but there was another loud crack, and Narcissa’s wand too flew into the air and landed on the other side of the room.

“You dirty little monkey!” bawled Bellatrix. “How dare you take a witch’s wand, how dare you defy your masters?”

“Dobby has no master!” squealed the elf. “Dobby is a free elf, and Dobby has come to save Harry Potter and his friends!”

Harry Potter and the Deathly Hallows – J.K. Rowling