Ryudamon: evolution tree
Fresh -> In-Training -> Rookie -> Champion -> Ultimate -> Mega -> Ultra hierarchy as told in Digimon Chronicle, from Yuji's Ryudamon through Ginryumon and Hisyaryumon to Ouryumon, which Alphamon turns into its sword to become Alphamon Ouryuken, plus the Ghost Game contagion into Gyuukimon.
Digivolution triggers
Alphamon Ouryuken: Jogress partner
Kota's Alphamon turns Ouryumon into its sword (Digimon Chronicle)
Lore notes
the stories behind the unusual arrowsPrototype Digimon
The Reference Book presumes Ryudamon to be a Prototype Digimon holding the combat data of Japanese myth's dragons and generals. In Digimon Chronicle, it seeks ever more fighting power.
Yuji's Perfect Pendulum
In Digimon Chronicle, Yuji sends the Rookie Ryudamon against UltimateBrachiomon and nearly loses it until MetalGarurumon X steps in; later, wounded, he still fires the X-Cast through Ryudamon to win.
The Ouryu Legend
A legend new to the New Digital World tells of the Ouryu, a dragon unknown in the old one, which an aquamarine wakes into a savior. Yuji and Ryudamon end their journey east with its power.
The Orbs of Hisyaryumon
Hisyaryumon's two crystal orbs hold the souls of its lost companions, Kinryu in the right hand and Kakuryu in the left; it stays calm as a god unless one is harmed.
Ouryumon's Sacrifice
In Digimon Chronicle, Ouryumon dies shielding Alphamon from Dexmon, and Kota's Alphamon turns its data into the Ouryuken; in Digimon Chronicle X the two fuse again against the seven Diablomon.
Ryudamon in Ghost Game
In Ghost Game, a Ryudamon bitten by a Gyuukimon turns into one and seeks Hiro's help to return; restored, it digivolves into Ginryumon to save Gammamon.