Giygas

Giygas, also known as Giegue in, is the main antagonist in Mother and EarthBound.

Giygas was raised from infancy by a woman named Maria and her husband George, both of whom were abducted from Earth in 1906. During this time, George studied the aliens' PSI powers without their permission, culminating with his escape back to Earth.

In
In Mother, Giegue invades Earth, abducting parents and sending other aliens and robots to attack people, especially Ninten. His first attempt was to have Ninten's lamp assassinate him, but this failed attempt leads Ninten to start his journey, discovering who Giegue is, and what relation he had to his family.

Atop Mt. Itoi, Giegue is confronted by Ninten and his companions. Before the fight actually begins, Giegue seems to offer to spare Ninten's life out of respect for Ninten's great-grandparents who raised him, asking him to come with him back to his planet. Ninten declines, and after being turned down, Giegue attacks him, and is invulnerable to every attack.

After Ninten and his friends sing the Eight Melodies multiple times, Giegue is forced to retreat as the emotional stress becomes too much for him to handle, promising to return and attack again.

For clarity, the player cannot name a character Giegue.

In-game description
"(Ninten hears the voice of Queen Mary) Giegue cannot be defeated with force... You cannot defeat Giegue with a weapon of any kind. You must SING my lullaby, with all your feelings... SING my lullaby with all your heart."

In EarthBound
In EarthBound (the subtitle of which is "The War Against Giygas"), Giygas has ruled the world ten years into the future, and uses the Apple of Enlightenment to see further into the future. Giygas witnesses his defeat at the hands of Ness and his party, and sets out to prevent this from happening.

Ness hears about him from Buzz Buzz, who came from the future to warn him about Giygas' plot. Shortly afterwards, they are both attacked by one of Giygas' henchmen, a Starman Junior.

Ness goes through all of Eagleland to harness his powers in order to defeat Giygas, and gains three fated companions - Paula, Jeff, and Poo - along the way. Giygas must be fought in the past, and to go there, the Phase Distorter must be used. The third such vehicle brings the party to him, with them becoming robots in the process. Similar to Giygas's appearance in, he can only be defeated by prayer. When finally defeated, Eagleland will be free of monsters, and can be explored freely, until Ness talks to his mother, which will end the game.