[Lore Concept] The Lost City of Crohha

Long time ago, there was an infamous city of Crohha. Inhabited by wizards, witches, elemental sages and all other kinds of magical people, yet, the city was known not for that. The thing, which went around Runeterra, from person to person, was a rumor about a demonic prison, where dark spirits were imprisoned. And while there were many different rumors about this prison, the existence of it wasn't a rumor - it was a fact. When city was built, new and fresh, the prison was already there, older than any other building in the town, magicians and witches used it to imprison demons and all other evil spirits they could find.

No one really knew how these demons were captured and imprisoned, what kind of magic were used. Only the magicians, who captured these demons, knew these secrets. Over hundred years, many different demons were captured, including 10 Lords of Sins, the most powerful demons know to men:

• Lord of Vanity - creature, born out of a blessed mirror, but was corrupted by demonic essence, twisting it into horrible form. Demon, who lives to expose weakness, darkest wishes and feelings, who feasts on horror and pain of mortals.
• Lord of Greed - a demon, who fashions itself with bones of monsters and animals. Very mysterious, while being very intelligent and cunning, this demon acts more as a wild animal, tearing attacking anyone in sight, tearing them apart.
• Lord of Envy - poor blooded demon, who traveled from the underworld. He envy lives of mortals, simple and beautiful, so he takes them them away, killing mortals, watching them die slowly, painfully, as he enjoys every moment of it.
• Lord of Fear - one of three female demons, she is passionate and wild. Made purely out of metal, no mortal weapon can even leave a scratch on her, while she enjoys breaking weapons of mortals, corner them and feast on their fear, as she takes away the hope from their hearts.
• Lord of Rebellion - second female demon, but entirely different from the first one. Calm, collected, always plotting something, always things three steps ahead of everyone. She represents the grandest rebellion there could be - a rebellion against death, as she is the most powerful necromancer there could be.
• Lord of Despair - the lindworm. He is half dragon, half demon. Strong, dark, malicious, he is the despair itself, as even his breath is poisonous. No normal mortal could ever be in his presence, as even being close to him, you would be poisoned to death in seconds, without him doing anything.
• Lord of Thirst - the strangest and most mysterious of all other demons. He was knows to kill mortals on the spot sometimes and other times helping them to do what they want. Not even other lords of sins knew what he is or why he does something. Only one thing was certain - wherever he went, massive storms followed him.
• Lord of Sorrow - the third female demon, maybe the saddest one of all other lords. She was born as a human, yet through terrible twists of fate, she ended up becoming a demon, bringing sadness and grief the every living creature around her.
• Lord of Pride - maybe the most unusual demon between them all, he cowered himself with armor, not showing even an inch of his true body. Also, he wields the Eternity Blade, the heaviest and most destructive weapon known to mankind. And he wields it with ease, like it doesn't weight anything.
• Lord of Rage - a living inferno or hatred, rage and bloodlust, he is the flame of destruction, yet, in his wake, ashes are reformed, brought back to life as remnants of his power. Without a form, he possess mortals, live inside of them until his vessels burns to crisps from within.

This city was well known and many powerful magicians living in it, yet, one day it disappeared from the face of Runeterra without a trace. Witnesses said they seen great number of crows, from thousands to millions, flying towards this city. Other, whisper about a demonic crow god, massive demon bird, who took this city right to the underworld or entirely separate dimension. However, no one really knows what happened, as no historical documents remained, to depict this even. Only rumors flew through people, but even those disappeared, as time went by.

Now, after great number of years, something started to change, something started to move. Travelers started to see things, talk about them to other people. They tell about unusual thing: about massive number of crows swirling about certain locations, about echos of screams and fighting, about strange chill in the air and about horrifying shadows.

People have forgotten about this city, about demons, who were locking inside of it. However, now they will be forced to remember, people will be forced to know the vile beings from this city. Runeterra will learn to fear and cower, as these Lords of Sins will emerge back into the world one by one.