- Obtain the Mine Gate Key and take it to Headstone Mine.
- Mine Gate Key: 0/1
- "The note you found suggests that the Mine Gate Key can be found at Sledge's Safe House to the north."
Once the mission has been accepted, the next step is to take the transition into the Arid Hills. A number of skags a short distance beyond the transition will present the first obstacle and several groups of bandits beyond them also bar the way. Sledge's Safe House lies to the north beyond several of these encounters.
Sledge's Safe House is a sprawling interior zone with a large circular room at the end where a boss battle takes place.
Medical and ammunition Vending Machines just inside the door provide the last point of sale before moving through this area. Further supplies must be gained from drops or chests beyond the first few fights.
Part of the way through the building a disabled Claptrap can be found, which will offer the mission Claptrap Rescue: Safe House. The quickest way to handle this side mission is to reach the robot through a barred opening before heading up the ramp to the next stage, thus avoiding the need to double back for the Repair Kit in the room directly above. It is worth doing this immediately due to the Backpack SDU reward, as well as the remote location of this Claptrap rescue.
The rest of the area is swarming with bandit encounters of all types. Badass Psychos can prove to be troublesome in games with higher player counts when they charge into melee, leaving limited evasive options in the confined space of this area. There are also several set piece battles, including one where a siren heralds the approach of a pack of Mutant Midget Psychos, and another where the final boss, Roid Rage Psycho will attack in conjunction with a small horde of midgets.
The conventional strategy for the boss battle is to keep running, killing the midgets first and taking shots at the Roid Rage Psycho whenever practical. He will charge and will also throw MIRV or Bouncing Betty grenades, thus emphasising the need to stay mobile. Killed Vault hunters will respawn away from the arena and may have the opportunity to re-engage without having to drop into the pit, although this generally requires being able to shoot past the fence rather than through it.
The Roid Rage Psycho can be set alight, so incendiary damage weapons can also be effective to keep him burning during run-and-gun fighting while avoiding contact. Corrosive weapons can be employed to similar effect.
Another way to beat the boss is to kill all of the midgets and then jump back into the small pit at the entrance. This can sometimes lure the boss into the pit where he will have trouble getting out, although attracts an element of risk with his grenades likely to land in close proximity of any characters in the pit at the time.
Another strategy is to shoot through the fences right behind the pit with a sniper rifle. They don't stop bullets like the one right in front of the pit.
After the Roid Rage Psycho is dead, a button becomes available near the center of the room. Pressing it causes a key to rise from an aperture in the floor.
A platform then extends across the pit. The fight back through the safe house, will not be any easier than the fight coming in, but some new doors will be open allowing players to choose a different path. It's shorter, but just as dangerous per room. The advantage of the new route is that it will have additional loot to pick up.
- "When the grisly 'key' is placed on the thumbprint scanner, the gate unlocks. Now that you can enter Headstone Mine, it's time to take the fight to Sledge."
- The text on the Mine Gate Key reads: A keyring of thumbs. Opens the Headstone Mine Entrance. Evidently the bandits needed the thumb prints of their former captors, so they simply took them.