The new Risk of Rain update came out, and with it, a new survivor! They look really cool to play, swinging around like Spiderman and punching enemies with giant steel fists. But I have no idea how to unlock them.
The achievement for their unlock is to defeat the hidden boss of the new stage, Siren's Call. I've looked everywhere in the stage and can't find where this boss is hiding. I assume it has something to do with the locked door and the similar looking flashing light nearby, but I don't see how to solve the puzzle.
