A bipedal mecha that is able to walk on walls and the ceiling. Despite the small size of its cockpit, it can hold and release a myriad of smaller devices with which to attack the player.
In order to fight this enemy, the player must choose "Go after Deadeye Joe" at the end of the first level, and then "Surrender and fight later" when they get ambushed by Colonel Bahamut and Dr. Mandrake.
In the last stage of that route, Space Station, Dr. Mandrake will teleport in place while riding the Mach 777 and attack the player as they are riding a very long elevator which connects Earth to Bahamut's station in space.
The fight consists of two main phases:
- First phase
At the beginning of the fight, the vehicle will start leaping across the room, landing on either the elevator's floor, walls, or ceiling; stay on the corners in order to avoid it. After the fourth jump, it will remain on wherever surface it landed last, open its cockpit, and unleash any of the following attacks:
- Sends out six flying devices which quickly take a position and let out a fire blade while rapidly spinning in place, then all devices reposition themselves at a random spot and repeat the attack. After about four times this attack is performed, the boss will start leaping inside the elevator again.
- The mecha opens its cockpit and starts releasing a multitude of small Mach 777s. Stay right below the boss and fire at an angle in order to both remain safe and inflict damage.
- Second phase
The boss will start walking inside the elevator in a clockwise direction, so keep circling around it by climbing on the walls and ceiling in order to avoid it. As the mecha keeps walking, its legs will start growing more and more, effectively reducing the space in the lift for the player to maneuver as the battle progresses. Just keep firing at the cockpit at every opportunity and the boss will eventually be destroyed.
The elevator will reach its destination in space only after defeating Mach 777, allowing the player to fight this route's final boss: Big Magnum.
The walker comes out of a Pill in the Weightless Elevator level after the Elevator Slug. It walks around the elevator and fires off curving and rebounding shots. After it takes enough damage, its legs will blow off and it will start hovering around while firing off curving rockets that can be shot down.