the thing about the corruption wave is, I wonder why homeworld never returned to take the earth after defeating nearly all of the remaining gems. Maybe they knew they wouldn't win, and the earth wasn't worth it, so they just... gave up. or maybe, the "damage from the diamonds" left the earth ruined in some way. also it's interesting that in centipeedle's drawing, there are only three diamonds, not four. maybe the removal of the fourth (pink) diamond happened earlier than we thought!