Sorry Bad Grammar and Spelling.
 
Part one: The war  
She is from the far east. She is the Ruler of the Kirin(Unicorn Version), Longma(Pegasus Version) and the Qilin(Earth Version). But In the past they where two Emperors. One for Kirin and one for the Longma. They being in war for 1000 of years for a land that Its call Tian where is the Kunlun Mountain, a Mountain that Grows the sacred Fruit, The Peach Tree of Wisdom a Delicious Fruit, that heals and brings harmony to the soul. The Quilin are the care takers of the Trees and there home is on the Mountain, they have no part in the war and they have no Military (think like the Buddha Monks). The War took many years and Destroyed Kunlun Mountain and barely Wipe out the Quilin, the ones that can Grow the Peach Tree. Now The War was to protect the Quilin that they are now only 7 left, But the land is Destroyed and the Quilin Can’t Grow a Peach Tree anymore because the balance of the land is Broken. The Emperor of the Kirin and Emperor of the Longma made a truce and unite their kingdoms. But to do that they need The Emperor of Kirins’s Daughter Yin and The Emperor of the Longma’s Son Yang to be wed. This might bring Harmony to the land and the Peach Tree of Wisdom will Grow once more. But The Problem is that Prince and the Princess are not in love of each others in Fact they hate each other but to bring balance to the land they let the arrange marriage to happen. Years have pass and the Peach Tree is still not growing.
 
They only gave Birth to unwanted, Unlove Daughter Princess Yin-Yang.
 
Part 2: Search for Harmony  
When Princess Ying Yang was born she never got the love that she deserve, her parents never love her because she was born for a reason that fail. But she never felt the love of her parents but she felt the love of her servants, they took care of her and love her, her people that still think she is hope and to harmony to this land, worship her and love her.
 
Years has pass and she became the Empress of the Kirin, Her loyal subjects cheer for her and love her. The Empress Love them too and she see that are suffering, she see the peach tree is not grown and food is becoming hard to get. To help her People she need to find another land, Empress Ying Yang conquer all the lands to find the soil that can grow the peach tree, they find food and new land but is not enough for Empress Ying Yang, She want harmony and want land that can grow the Peach tree. Empress Ying Yang has conquer many lands but none of them can grow the peach tree. One of her soldier found a place that grows apples the Empress of The kirin never heard of apples but she took a bite of the apple that her solider brought, It was Delicious, The Empress was motivated when all hope is lost, She ask her solider where is this land? This is the place that has Harmony a place for the Peach tree to grow.  
The solider reply that is call Equestria. The Empress of the Kirin Yin Yang say this land we must conquer it and it will be the land of the Kirin! Her people Cheer for of joy and march to the land of Equestria.