Giallo was one of the Sages that stood by Ghetsis and claimed the Pokémon were enslaved by humans. To free the Pokémon from humans, Ghetsis sent Giallo to find more information about the Legendary Trio: Tornadus, Thundurus and Landorus.
Black & White arc
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Black 2 & White 2 arc
When speaking to Blake, Leo remembered the Seven Sages that caused trouble during the Unova Pokémon League.
Blake reported to Looker that Giallo was seen around Aspertia City. Once Blake faced a Tornadus, Looker believed it was Giallo, who used a mirror to transform Tornadus. Giallo was chased away by Tornadus and started to curse Colress, who actually captured the Legendary Pokémon and declared himself as "the new king". He sent Krookodile, who was quickly defeated by Tornadus that snatched and carried Giallo away. However, Blake stepped in and had his Keldemaru and Dewott defeat Tornadus by freezing it. Giallo complimented Blake's tactics, but was soon arrested by Looker. Before Looker took Giallo away, he and Blake asked of him did he knew Whitley. Giallo denied ever seeing the girl and was soon arrested.
Zinzolin told Colress how none of the Seven Sages knew nothing of Kyurem, which was why he shared the info about Kyurem with Team Plasma.