The Devil's Machine is a massive device that appears in EarthBound, and serves to contain Giygas and his tremendous power and stabilize his mind. During the end of the game, Ness and company enter a hole in the Cave of the Past, which leads to a room composed of several pulsing "flesh" tubes; the tubes converge at the end of the "room" where the machine's 'core' (and Giygas) reside. Approaching him causes Ness's face to appear on the machine, and Pokey Minch appears in his spider mech, taunting the party before beginning the final boss battle.
During the battle, the Devil's Machine effectively makes Giygas invincible, as it counters any attack that hits him and deals double damage to the attacking party member(s). Once Pokey's HP is depleted, he decides to shut the device off, unleashing Giygas' power and destroying it. The result is a chaotic, bizarre dimension that traps Pokey and the four children in darkness until Paula's prayers eventually defeat Giygas.
Giygas cannot be harmed in any way due to his shield. The best to defeat Giygas and Pokey is to put up a shield of your own. At the beggining of the battle, have Paula put up a PSI Shield Σ to stop Giygas' PSI Rockin attack (DON'T put up a β or higher shield, as it's reflective abilities will devastate your party). His shield can only stop attacks, so it is still possible to steal PP from him. If the shield wears off, put up another one immediately. Then all you have to do is focus all your attacks on Pokey.
- If Giygas was defeated and the Debug Menu is used to enter Giygas's Lair, it will be possible to fight him again as if the game weren't completed yet.