The 100 Years Of Exile is a time period that occurred in the HERO: The Guardian Smurf story series that lasted for 100 years. It all started when Hero gained his special Ki powers at the young Smurfling age of 50 and almost killed his fellow Smurfling, Jokey, who played a prank on him and accidentally called him a power mad freak, which caused him to go on a rampage and badly injure Jokey closely to the point of death.
Papa Smurf had no other choice but to exile Hero from the village, and wouldn't allow him to return until he was fully capable of controlling his new powers. Hero then met Master Kai whilst out in the forest trying to build a temporary home for himself, away from his fellow Smurfs. Master Kai knew that Hero was the current owner of the Power Stones and he decided to take him back to his own dimension in order to fully train him in the control and proper use of his newly found abilities.
Hero returned at the age of 150 and rescued his fellow Smurfs from the evil wizard, Gargamel, after his close friend Hawkeye was kidnapped by the wizard for the formula for the Philosopher's Stone.