The first King of Hoenn had no fear of losing his throne to rebellion nor a dagger in the night, for his army was strong and his pokemon stronger. But he had made countless enemies in the process of unification and was terrified of poison. And this fear was justified, for he ran through so many human taste-testers that even he became unnerved by the carnage.
The Lord of Petalburg was implicated in a poisoning attempt and sentenced to die by tasting the king's food. To save his life, he told the king of a species of pokemon called Breloom which was healed by eating poison, yet was not a poison-type so meals could be shared safely. The king pardoned him, but seized one of his Breloom for the task.
For five years, this Breloom was imprisoned in a cage except during meals and beaten by the king's pokemon guard, so that when he was released to test the king's food he would be able to regain his health. He called constantly for the Lord of Petalburg, now an important noble at court, but he could not respond for this Breloom was never both free from his cage and far from the king's side.
At one feast, the king commanded the court's pokemon battle for his entertainment, and the Lord of Petalburg took his chance. He entered his second Breloom, which opened the match with Double Team and in the confusion switched places with the king's taste-tester. This Breloom had the other ability of its species; it was not healed by poison, but spread poisonous, stunning, or sedative spores into otherwise harmless items. When the king made him taste his bread, it became poisoned; when the king ate the bread, it killed him and his kingdom vanished into civil war.