Cyrus is Team Galactic's leader.

He made his first appearance in Losing Its Lustrous! and Double Team Turnover!, along with Mars, Jupiter and Saturn. It was revealed that he is a rich businessman who has made most of the buildings and libraries throughout Sinnoh. However, Ash and the others do not know that he is also the Team Galactic leader. Using his businessman alter-ego, he visits the Celestic Town Historical Research Center while the remaining members of Team Galactic carry out a plan to steal the Lustrous Orb from the Research Center, after having already stolen the Adamant Orb from its Eterna City police escort.

He discovers from Ash and Dawn that they have seen Azelf and Mesprit when the two tell of their encounters with the mysterious Pokémon at Lake Verity and Lake Valor, which apparently intrigues him

He appeared again in Saving the World From Ruins!. He was seen in Team Galactic's headquarters alongside Saturn and Jupiter as well as Charon. They were coordinating Mars's mission on Iron Island and using a beam launched with the Spear Key to scan energy readings from the Spear Pillar. However, Mars's machine was destroyed when the scan had reached only 60%, presumably ruining their mission. Despite this, Cyrus did not appear to be discouraged.
Cyrus takes control of Dialga and Palkia with the Red Chain

Cyrus also appeared towards the end of Unlocking the Red Chain of Events!, where he requested J's services in capturing Uxie, Mesprit and Azelf. In The Battle Finale of Legend!, he takes control of Dialga and Palkia, and steps into a portal created by the two legendary Pokémon. The portal soon got destroyed, leaving Cyrus's fate unknown.