The prosperity ritual appears to be a sacred or religious ceremony revered by the Black Arms, evidenced by the various words and titles used by Black Doom to refer to the event, like the "day of reckoning". It refers to when Black Doom brings the Black Comet down to Earth with Chaos Control so the Black Arms can take over the Earth in order to use the human population as a food source.
Black Doom appears to have been planning the prosperity ritual for at least the past two thousand years, having brought the Glyphic Canyon temples to Earth in order to use them as weapons for that day. Over fifty years ago, Black Doom would help Gerald Robotnik with Project Shadow, a medical research program to create the "ultimate lifeform", by donating his own blood to the creation of Shadow the Hedgehog, so the alien overlord would have an agent to assist with the prosperity ritual.
Shadow the Hedgehog
Fifty years after Shadow's creation, Black Doom began setting up for the prosperity ritual by having his Black Arms invade the modern-day earth. Black Doom then set Shadow on the path to collect the seven Chaos Emeralds for him which he would need to teleport the Black Comet down to earth with Chaos Control, as the comet would not withstand atmospheric entry. In the end, the prosperity ritual was commenced when Black Doom got the Black Comet down to earth as planned and began spreading a paralyzing nerve gas to immobilize the planet's population for his spawn. However, Shadow rebelled against Black Doom and destroyed him, before sending the Black Comet back into space as Super Shadow where it was destroyed by the Eclipse Cannon, foiling the prosperity ritual.
- Sonic Team (15 November 2005). Shadow the Hedgehog. GameCube. Sega. Area/Level: The ARK. "Black Doom: The seven Chaos Emeralds are needed to demonstrate its full power, or tomorrow's prosperity ritual will be for nothing!"
- Sonic Team (15 November 2005). Shadow the Hedgehog. GameCube. Sega. Area/Level: The Last Way. "Black Doom: Let us begin our ritual of prosperity. Chaos... Control!!"
- Sonic Team (15 November 2005). Shadow the Hedgehog. GameCube. Sega. Opening Cutscene. "Black Doom: As you can see, the day of reckoning will soon be here!"
- Sonic Team (15 November 2005). Shadow the Hedgehog. GameCube. Sega. Area/Level: Sky Troops. "Black Doom: I transported this brilliant flying fortress to this planet over 2000 years ago."