After you best Cyrus for the last time you never see him again. The last place you ever see him is the distoration world. Did he choose to stay in a world with nothing in it if he couldn't make a perfect one?
After his defeat at Spear Pillar, Cyrus claims he will have revenge and disappears. His assets and duties are left to Saturn.
Sorry but Bulbapedia has only information about Diamond and Pearl.
When you defeat Cyrus in the Disortion world, he never stays in that world, he just lives off as a normal person, but his dream never came true. (Hope This Helps!)
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