After hearing the voice, return to the starting room. The next step requires a bit of luck to get a bomb. If that happens, it’s probably best to reset. Note that if you get ‘Curse of the Labyrinth’ on the first floor, you’ll have to defeat both bosses. If you’ve done it correctly, you’ll hear Mom shout Isaac’s name followed by the sound of running footsteps. Pressing Tab will change the minimap and allow you to see just how much time you have. The first step to unlocking The Forgotten is to reach and defeat the first floor’s boss in one minute. Cain is also a good choice, due to his decent health and attack combined with having the highest base speed of all the characters. He doesn’t start with any heart containers (instead getting 3 Black Hearts,) but he moves fast, flies, and can do good damage with his short-range Brimstone attack. Out of all the characters in the game, Azazel is probably the best choice. This means that you’ll want to choose a character that can move and kill fast.
Part of the requirements for unlocking The Forgotten requries a good bit of speed.
