The Ice Age

Fix the time machine to unlock the Ice Age, the first area on the alternate timeline path. This requires completing a multi-step quest involving the Cryogenic Time Chamber from Dr. Beanies. You must take the chamber to the Throbbing Domain in Act 1 and use it to capture the Throbbing King's heart. Once the time machine is operational, you can travel to the past and explore the frozen Ice Age landscape with its prehistoric enemies.