In 1973, Bardeen, Carter, and Hawking conjectured the “third law” of black hole thermodynamics: a subextremal black hole cannot become extremal in finite time—the black hole analogue of Nernst’s unattainability theorem in classical thermodynamics. After reviewing basics of extremal black hole geometry, I will discuss some history of the third law, its various formulations, early counterexamples, Israel’s (flawed) 1986 proof, the intervening dark years, and its eventual disproof (in some settings, see Reall’s talk!) in my joint work with Kehle.