HANDY TIP: If you're having trouble navigating through Mysterious Mine, I highly recommend pressing Tab to pull up the world map. This will allow you to see all of the tunnels around you, and navigate accordingly. You can even move while you're looking at the map.

- There are three entrances to Mysterious Mine. The first is near the beginning of Choppy’s Woods, past a yellow duck and through a tree that’s a short ways east of the button where you speak to Fredbear. The second is in the far northwest corner of Dusting Fields, just after you defeat the Bouncer. The third is again in Choppy's Woods, though you need to go through Lilygear Lake (specifically, hug the beach as you head north from the entrance) to find it.

- More new enemies! Huzzah! This place is, on average, a substantial leap up from other areas you’ve explored. If you haven’t done much with Bytes yet, I suggest buying a few. Getting the first endoskeletal upgrade back in Fabear Hills, Reinforced, isn’t a bad idea either. Withered Bonnie’s Unscrewed 2 attack is really helpful here for killing these durable enemies in a single hit, if you’re having trouble. You can expect to face the following guys while wandering the Mysterious Mine:
  • Quarries. These hefty rock men only use straightforward attacks, but they hurt. A lot. They’re fairly resistant to normal attacks, so heal often and employ lots of status ailments. Instant death attacks such as Unscrew are quite useful against Quarries, as are the Reaper Bytes.
  • Goldmines. Honestly, they’re almost identical to Quarries in what they can do, and are just as tough. Goldmines don’t give any experience, but they do drop a nice amount of Tokens.
  • Metalmen. Basically more spastic versions of the Chop ’N Rolls from earlier in the game. They’re pretty harsh in large numbers, and you should try to stun them to slow their attacks. 
In addition to all of the above, Mysterious Mine seems to be a pretty awesome place to pick up new animatronics. Be ready for many a scrap while wandering in the dark.

- We’ll start with the Choppy’s Woods entrance, as it’s not connected to the Dusting Hills sections. There’s not a whole lot to see here, as the passages winding around the entrance are all dead ends. Take a left at the entrance, go south, take another left, go south to the edge of the map, and go left again. You’ll see a large, golden chest down a nearby tunnel - and you might want to save, because an unseen boss will attack if you walk towards the chest.

The Eyesore of Mysterious Mine in FNaF World.

Y’know those Unscrew attacks you may or may not have been using to get through this Mine? They’re about to come back and bite you in the butt. Eyesore has two attacks: either he hits for around 100 damage - no big deal - or he uses Unscrew. If he uses Unscrew there’s a great chance one of your characters is about to die. If this keeps happening your party will just sloooowly disappear. The key here is to more or less ignore defence and wallop him with every powerful, single-hitting attack you’ve got. Stunning Eyesore also helps you get in more turns before his next insta-kill attack, and poison attacks will allow you to whittle him down more quickly. Not a complicated battle, but hard enough. (Especially since you don’t see it coming.

The chest Eyesore is guarding contains an Endless: Speed Chip. Nice. That, however, is all you can find in this part of the mine.

- Mysterious Mine branches in three directions at the Dusting Hills entrance. To the left you may find some Tokens; to the right is a dead end. Forward!

- There’s another intersection ahead. North is a dead end; right is a dead end. Take the left and the path will split again; go north. You’ll wind up at yet another intersection with a red chest sitting above the path. You can’t get it, but if you go north beneath it and head west you’ll find another golden chest protected by an Eyesore. The chest contains the Auto: Giftboxes Chip.

- Make your way back south, beneath the red treasure chest, and head east. Once you hit the edge of the area, head south and keep following the passage as it twists northwest. There’s another gold chest waiting nearby, as well as its mandatory Eyesore defender. The chest contains an Evercomet: Strong Chip.

- Now for the final entrance. Head to Lilygear Lake, head north from the Jump point into Choppy's Woods, and wander northwest until you find the entrance.

- There's, surprise, an intersection ahead. The entire eastern route is both long and utterly useless, so skip it and take a left. Head northwest and you'll find a tunnel that leads to a Lolbit's Byte Store. This one contains the Block5, Block20, and Block50 Bytes. I think these Bytes block as much damage as is displayed on the Byte per hit, but I can't say for certain just yet.

- Head back south towards the intersection, then move towards the southwest corner of the area. You'll wind up dipping into the darkness at the side of the screen. You can move through it and along the edge of the screen far to the north. Eventually an eastbound passage will pull you back out into the light.

- Wander around in the northern tunnels. You'll find two golden chests up here, only one of which is guarded by an Eyesore. The first chest contains an Endless: Strength Chip; the second chest contains an Endless: Defense Chip.