Authors Note: this is my take on what would happen in the third rune war, if it happens. Sorry in advance if you see grammar/ lore mistakes, this is my first story. Enjoy!
Prologue
Katarina looked ahead onto the horizon. The dust gathered, she saw the Demacian troops making camp. 3 days earlier, the league had collapsed. Archsummoners and summoners alike were slaughtered in an assault by voidlings in a abyss opened by Malzahar. Caught by surprise, the power of the League of Legends had diminished overnight. Immediately after hearing this news, Swain had chosen to declare war on Demacia and Ionia. The Noxian High Command, thirsty for blood and revenge on the two nations it had failed to conquer the last rune war, agreed. Katarina unsheathed two of her blades strapped to her hips and licked her lips. "This was going to be a good fight," she thought.
All across the Demacian pavilion, soldiers were readying for battle. A corporal stumbled as he ran into Garen, the Might of Demacia, overseeing the soldiers. The Demacian military had quickly responded to noxus's declaration of war, gathering the soldiers who had returned home in peacetime. Now the Demacian army, thirty thousand strong, were about to march on to meet the Noxian forces in a clash of fate to determine who truly would be victorious. "Garen, get in here!" shouted Jarvan IV from his makeshift tent. Garen, with an anxious look on his face, jogged to Jarvan's tent to discuss battle tactics.
The Ionian troops were ready to march. "We might not be the greatest military power, or have the most soldiers, but for what we lack in numbers we shall make up with our fury!" Irelia shouted to the troops. " We will defeat Noxus, and finally conquest the bloodlust of the Second Rune War!' The army cheered, and many began clanking their weapons. "We depart for an attack on Zaun tomorrow," Irelia told Karma. "The Noxians are busy approaching Demacia, and Zaun creates much of their weapons and technologies. That leaves Zaun undefended, and without any allies Noxus will soon fall to our alliance. We have sent envoys to Piltover, Bandle City, and the Frejlord. They have little reason to not join our cause." Karma frowned. "I have heard rumors that the Institute has fallen somehow. That is why noxus is declaring war. That leads me to fear. What could have destroyed the institute?" " No major threat, Karma" Irelia chided. "Our main objective is to crust Noxus. Besides, they are only rumors. I'm sure nothing has happened to the institute"
In fact, something was very wrong. At the smoking ruins of the institute of war, Kha Z'hix was gnawing on a human skull. "This is only the beginning," he hissed in his soft raspy voice. 'Soon, I will have enough power to unleash the full power of the Void. What has happened here is only the beginning." Malzahar chucked to himself "Oh, what can measly city states warring against each other do without their puny summoners to protect them?"