Short answers, pulled from the story.
Space Runaway Ideon is set in the year 2300 on the planet Solo located in the Andromeda Galaxy. The story begins when archaeologists from Earth restore three massive armored tanks that activate upon the arrival of the Buff Clan.
The three children in Space Runaway Ideon are Piper Lou, Ashura Nobaku, and Fard Maraka. These orphaned children serve as the catalysts for the Ideon's power and their survival is central to the plot.
Karala Ajiba dies at the hands of her own sister Harulu during the conflict. Her death triggers the Ideon's power to wipe out both civilizations and seals the fate of the universe.
Sheryl Formosa suffers a psychological collapse after the deaths of her sister Lin and her lover Gije Zaral. Her obsession with understanding the Ide leads her to make decisions that provoke the Ideon's full power.
The final confrontation ends with the total erasure of both the Solo Ship crew and the Buff Clan. The Ideon uses Karala's unborn child as a trigger to destroy both races and reset the universe.