This page gives a summary of Demacia and its history in Factions. More information is available on the Demacia page in the League of Legends wiki, which can be found here.
One of the two superpowers remaining after the Rune Wars, Demacia has pledged the full measure of its strength to defend the innocent and destroy the cruel, whatever the cost. Even in the world-rending chaos that preceded the founding of the League of Legends, Demacia was greatly admired for its willingness to intervene on behalf of the weak, protecting those who had no means of repaying them. The League itself could never have arisen without Demacia’s support, and it now seeks to use the Fields of Justice (you just know that a Demacian was involved in that naming process) to right wrongs across Valoran. In times of catastrophe, the sight of the Demacian flag is a cause for rejoicing. Children from many nations tell excited stories about brave Demacian knights vanquishing demons and capturing villains—though their elders often find themselves frowning at their children’s simplistic image of a kingdom driven by fanaticism untempered by basic humanity. Scholars of the arcane trace Demacia’s veneration of the element of light to ancient Shuriman solar magic, but note the drastic simplification those teachings underwent in Demacia: stripping away the sun’s warmth, leaving only its blinding light.
Though a great force for good, Demacia has also wrought much destruction in its uncompromising pursuit of its ideals. While it selflessly intervened to protect weaker nations in the Rune Wars, its obsession with the eradication of its hated enemy Noxus also drove the Rune Wars to new heights of catastrophe. Where more moderate minds might have found room for compromise, Demacia would accept only complete submission to its demands. Often, those it protected would swiftly find themselves scoured by the relentless investigations of Demacian inquisitors. These inquisitors were free of any trace of corruption, wholeheartedly devoted to the purest conception of justice, and unimpeachably impartial—but also merciless in their judgments. Experiments determined too dangerous to continue were terminated. Books of forbidden lore were burned. Corrupted individuals determined too far gone to be redeemed were imprisoned or put to death. Its own citizens live under such harsh scrutiny. It is unquestionably a totalitarian state: its citizens are indoctrinated from birth, lives directed according to the dictates of Demacian law rather than individual desire. (There is only one significant exception: any Demacian who proves himself or herself worthy can become a knight of Demacia.) It must be emphasized that it is not a corrupt regime, nor are Demacian virtues a ruse to cover up the selfishness of the nobility: the high-born are scrutinized even more closely than the common folk, and short of charging at the king with a drawn dagger there is no surer way to invoke the terrifying force of Demacian justice than to abuse one’s position for personal gain. But while there is justice, there is no freedom.
The League era poses new challenges and dilemmas for Demacia. When Noxus invaded Ionia, then a non-League state, Demacia’s dedication to the rule of law prevented it from taking up arms against Noxus, its “fellow” League state. While Demacian advocates argued before the Council about the interpretations of treaties and urged the formation of adjudicatory committees to hear reports of war crimes, the legions of Noxus slaughtered Ionian civilians and razed great cities which had stood for thousands of years. It ended in diplomatic compromise, and Ionia endured nearly a full decade of Noxian occupation. Shortly thereafter, Demacia, not a nation familiar with careful brinksmanship, failed to control the Kalamanda situation, which erupted into a disaster that almost destroyed the League. Its poor performance on the Fields in the dispute over the Mirrorwater painfully underscored the fact that a nation almost unmatched on the battlefield might quite laughably fail in the League. Its subsequent victory in the Ceruleana dispute gave it an opportunity to bring order to Valoran, and it took it—only to discover that the cosmic balance would not abide such treatment when the sands of Icathia split open and the sinister forces of Discord nearly destroyed the League and its member-states. When Noxus invaded Ionia once more, it seized upon a right of naval intervention—and in destroying a Noxian invasion fleet also slaughtered thousands of Noxian refugees left homeless by the war against Discord.
Demacia participated in the Mirrorwater dispute, coming in fifth place out of five factions participating.
Demacia won Arc II, Ceruleana, out of 6 factions who participated. It gained ownership of the island and access to the supernatural sea goddess residing upon it.
During Shon-Xan , Demacia was not a participant in the dispute but did deploy its navy and invoked the powers of the sea goddess, Ceruleana, to smite the Noxian ships that were sailing to land troops on the Ionian island.
In Arc V, the Hextech Revolution, Demacia took second place out of the four factions involved. It deployed troops and mages to defend Bandle City from the attack of Nefara. Later on it called upon its allies, Piltover and Bandle City, who were both also in the dispute, to join it as it attacked Zaun's pyrikhos mines in the Battle of Shurima. It was heavily sanctioned afterwards for breaking the League's peace edict over the region.