There exists an ancient order originating in the Ionian Isles dedicated to the preservation of balance. Order, chaos, light, darkness -- all things must exist in perfect harmony for such is the way of the universe. This order is known as the Kinkou and it employs a triumvirate of shadow warriors to uphold its causes in the world. Akali is one of these shadow warriors, entrusted with the sacred duty of Pruning the Tree - eliminating those who threaten the equilibrium of Valoran.
A prodigal martial artist, Akali began training with her mother as soon as she could make a fist. Her mother's discipline was relentless and unforgiving, but predicated on the fundamental principle: We do that which must be done. When the Kinkou inducted her into the order at the age of fourteen, she could slice a dangling chain with a chop of her hand. There was no question - she would succeed her mother as the Fist of Shadow. She has had to do much in this role which others might find morally questionable, but to her it is in service of her mother's inviolable doctrine. She now works with her fellows Shen and Kennen to enforce the balance of Valoran. This hallowed pursuit has unsurprisingly led the triumvirate to the Fields of Justice.
Source: The Game Website.