We want to develop dragons in our lore, but this isn't a place I can really delve too deeply into them, sadly. Shyvana herself doesn't know much about dragons beyond what she learned from her father (dragons are dangerous, territorial, powerful creatures who look down on humans a great deal).
Like this mean S.O.B.?
The tale of Plagueis the Vile has long been a bedtime story to children of men and yordles. Over a thousand years ago, the mighty Blood Dragon plagued the lands of Valoran, destroying all that would oppose him and slaying any who dared to approach his lair of Death's Spire, a peak in the Ironspike Mountains continually shrouded by black clouds. As cruel as he was powerful, Plagueis' reign of terror lasted for 500 years, and all those who challenged him perished. That is, until he was challenged by a hero bearing the power of the sun. The two combatants fought for what seemed an age, until the hero called down the full power of the sun. Plagueis was struck down by his foe, and his blackened flesh crumbled to bones within his lair.
A thousand years passed, and though his body had been destroyed by the Solari hero, Plagueis' blackened soul remained through sheer hatred of all life. Were it not for the machinations of Karthus, the Deathsinger, Plagueis' bones may have remained as such. But the lich, discovering the dragon's final resting place through the League of Legends' resources, journeyed to Death's Spire and found the ruined corpse of the once-mighty black dragon. Arcane magic heeded the lich's dirge, and the soul of the dragon returned to its body. And despite the intervention of the League's summoners, who discovered Karthus' plan, Plagueis rose again, not alive, but not dead. Like the lich, Plagueis now had joined the ranks of the undead.
But to Karthus' surprise, he could not control Plagueis, as he had intended. The dragon, driven by hatred and malice, lashed out at all around him, and only with the intervention of Leona, the Radiant Dawn, were the summoners able to restrain the undead dragon in his lair. Yet even with the Solari hero's successor, the summoners could not destroy Plagueis, and were barely even able to contain the dragon in his bindings. Yet a solution was found by High Councilor Vessaria Kolminye, who intrigued the dragon with the prospect of "destroying anything he wanted", so long as he participated in the League of Legends. This offer has seemingly appeased Plagueis... for now...
There's not a shred of light to be found within his blackened soul. - Leona, the Radiant Dawn