The Mouth of Hell is an achievement in Diablo III given for exploring the following areas of Arreat Crater: * Arreat Crater, Levels 1 & 2 * Tower of the Damned, Levels 1 & 2 * Heart of the Damned * Tower of the Cursed, Levels 1 & 2 * Heart of the Cursed * The Core of Arreat * Heart of Sin