The Great Massacre

The Great Massacre (also known as "The Patsy Bloodbath") is an event that took place long before the Type Unity Law was in effect. It is first mentioned in Pokemon: Unlimited, where it is described as "the worst bloodbath in history". It was said that this event almost led to the extinction of certain Pokemon types, mostly Dark type Pokemon, with Dragon and Ghost types being a secondary event.

History
Before the creation of the Type Unity Law, victims of this massacre were Dark, Dragon and Ghost type Pokemon, with the Dark types suffering the most. During those times, anyone was allowed to kill their types without any repercussions. The three scarcely forbidden Pokemon types were also brought into slavery, only to be sold or killed by the highest bidder. Said to be shamed and ostracized by society, they were not allowed to get jobs, own places, or even live in the presence of any other Pokemon. They were also even hunted down by groups called "Banishers", which were Fairy type groups meant to represent justice and "Arceus's forces" in the world. It was said that even children under these circumstances were not spared from it.

What linked this to the massacres of the Dark, Dragon and Ghost types were based on rumors of their supposed "connection" towards Lord Giratina, who is known by generations of storytellers as "The Deadly Shadow", "The Phantom Leviathan", or "The Black Dragon". As a result, it created fear among many Pokemon, causing them to distrust their types and create a "segregated world" against them, not even being associated with them. However, the greatest death was the mysterious white explosion known as "Ultima", which was an attack said to be "viewed around the world", resulting in billions of deaths towards the Dark, Dragon and Ghost type Pokemon. This attack was also responsible for the destruction of three islands, which belonged to the victims of said devastating attack.