the binding of isaac afterbirth plus how to unlock lost?
The lost can be unlocked with seeded runs at any step of the process except for the final one. Isaac must die from a Mulliboom in the basement/cellar. A very easy seed to do this is CD2H NNRN, run around hurting yourself with the spiders, there's gonna be 3 mulliboms in there. Keep in mind you have to be in Hard.