Izo threw the note. It's saying: "I'm Izo, the resident of this labyrinth. I don't know how did you get here, but if you can't deal with horrors of this place - you'll die. Follow my commands and you will survive long enough to find an exit. I will stay out of your vision. I hope you'll understand why. Quick advice: if you hear closing-in noises that aren't the hums - keep your distance from them, if you find the source - run away until you escape them. And do not trust any human-like noise."