The Three Grand Dragoras are the Leaders of an undefined race of Dragons simply known as "Dragoras", one of which Dragoramon is part of. For the most part, the history revolving the three founders have nothing to do with Digimon, but rather, their relations to Dragoramon is what ties their link to Digimon Classic, as well as a few other cameos of various other Dragora individuals that appear. All of the Dragoras that appear take place in a flashback that is shown by mysterious DigiCores that are located throughout the Digital World. First, the flashbacks simply show silhouettes and minimal dialogue, but enough to get the point across that somebody is being punished for a great crime against the the Digimon Universes.
Dragora Galaxia, the original Dragora, was born 7 trillion years prior to anything else's existence. He is the most aware of the Dragoras, of how he can see nearly every universe's exact details. However, he knows he is too powerful for even his home universe, so for the most part, intentionally sealed himself into limbo until he was forced out by Dragora the Yami, the then current leader of the Dragoras. Due to the power he gained from his slumber, Galaxia was quick to put Yami in his place and make himself leader instead.
At the dawn of the Dragoramon Incident, around the end of Bursting Cries's storyline, Galaxia, along with many other Dragoras, are summoned up by Dragora moments after the latter impaled Dragoramon with the Omni Sword, as each of the Dragoras give a speech as to what kind of punishment that Dragoramon deserves for having become both far too powerful for his own universe, and also the fact he deliberately interfered with past events when the common rule was that no Dragora was to ever do such a thing.
Dragoramon, completely unaware of this, is smacked in the head with Galaxia's Black-Matter Staff, after which nearly every incident that had occurred beforehand was flashing through Dragoramon's mind. Dragoramon, still confused by what these mysterious beings are asking of him, asks who they are. Galaxia simply replies "Thy name is Dragora, for we are many.... All, except you, Dragoramon...". Infuriated, Dragoramon tries to off Galaxia, but is blocked by Dragora the Dark and Dragora the Yami, and further prevented from moving as Dragora shoves his Omni Sword further through Dragoramon's chest, sentencing him to limbo as he and all the other Dragoras fade away.
Dragora the Dark
|Dragora the Dark|
Dragora the Dark doesn't say as much as Dragora Galaxia does in regards to the Speech... No... He believes it's best for him to keep his mouth shut in all of this, since he does not wish to deal with traitorous scum such as Dragoramon... Yessssssss... As you can see, this entry on Dark is given solely based on his own personality, from which you barely see much of in the flashbacks he's seen in. Dark, however, is also the first of the Dragoras to actually be seen, whereas Dragora Galaxia remains in hiding during the events of Digimon Classic. However, do not be fooled, because while Dragora the Dark does appear for a brief moment, it's only a quick cameo, but one he hopes will at least give the main cast a bit of foreshadowing as to who the real villain is... Yessssss...
Dragora the Yami
|Dragora the Yami|
Dragora the Yami doesn't slouch around like the rust bucket that is Dragora Galaxia. FAR from that. He's more or less the only one of the three to take immediate, direct action towards his adversaries. Yami is by all means the most ominous of the group aside from Galaxia himself. Why was Yami the only one born as an Asian Dragon type Dragora? Why was Yami's heritage so hated by the other Dragoras? Was it because his kind could potentially be even greater in power than even the likes of Dragoramon himself? Nobody knows, but one thing is for sure, that even though he doesn't agree with Galaxia's plans, he does at least keep an eye out for anything bad happening. He cameos at the end of Digimon Classic as it's revealed a majority of the narration by neither of the main cast members was by him, only for him to be annoyed that his audience, Grandis and Mighty had been paying no attention to him whatsoever, much to his own personal annoyance.