Dragon (竜人; Ryujin) is a family premiered in BS01. Most Dragon cards are Red in color. While the English name simply refers them as "dragons", the Japanese name actually means "dragonoids", which is why all Spirits in this family appear to be dragons with humanoid figures. Archetypes in this family includes the "Dragno", "Dragron", "Dragonaga", and the "Ryuuman". On the collaboration side, the evolution line of Veemon and several other Digimons are majorly in the Dragon family.
Despite having many archetypes, for a very long time the Dragon family did not have a particular play style, nor did they have a deck dedicated to themselves. In the Ultimate era, the Dragon family has been getting more functional cards under the "Ryuuman" archetype, other than the occasional one card or two in the past. (Ryuuman-Fantasista to retrieve cores, The Burning Sacred Place of Dragons for protection etc.) They are given the role to support the Red Ultimates since the first SD in the era (SD19), and especially the Ultimate Dragon in the late era. The first Dragon family X-Rare, Ryuuman-Godbreaker, debuted in BSC15. However, the Ryuuman deck only started its development for real in BS30, with mainly Ryuuman-the-Formula being the leading card.
During the Rebirth era, the "Dragno" archetype was revived and given more support. With the help of the new mechanics, like the Grandstone Nexuses and the Pursuit keyword, the deck was able to gain a place in the meta.