Millions of years ago, Desghidorah first appeared on the planet Mars, destroying it and turning it into a wasteland. He then flew to planet Equestria with more intent to destroy it. He began attacking the planet, but he was met with a revolt. Desghidorah was defeated and locked away in a tomb in Tartarus
Queen Chrysalis went to the Desghidorah's tomb and caused it to rise from the ground. She managed to break it open and Desghidorah was released. Desghidorah rose from the tomb and began to absorb energy from the forest around him.
Princess Celestia and Princess Luna sent Twilight Sparkle, Rainbow Dash, Pinkie Pie, Rarity, Applejack, and Fluttershy to defeat him, but they were quickly overpowered. Ryan came to save his friends. Even with the combined efforts of Ryan, Twilight Sparkle, Rainbow Dash, Pinkie Pie, Rarity, Applejack, and Fluttershy, they couldn't defeat him.
Desghidorah harvested all the energy he could, then regrew his wings and attacked Canterlot. Ryan flew after the monster, and fought him with all his might, relentlessly blasting him, throwing wave upon of searing beams and energy blasts at Desghidorah, who could only feebly attempt to defend himself against these, the most powerful Prime-Prince of all time. Ryan attacked, surprising the relative of King Ghidorah and knocking him from the sky. Desghidorah roared in anger and rose to fight his foe, but the energetic Prime-Prince proved to be more agile than the three headed dragon. Confusing his opponent with his speed, agility, and rapid-fire techniques, Ryan was quickly gaining the advantage in battle. Desghidorah and Ryan struck one another head-on and Desghidorah was sent plummeting into the ground once more. After the long battle, Ryan managed to sealed Desghidorah back in his tomb in Tartarus.