One of the ruling Trinity of Equestria, alongside Princess Twilight Sparkle and Princess Water Lilly, Princess Cirrus Storm completes the Holy Trinity of Land, Magic, and Sky. Cirrus is also the eldest of the trio.
 
Born a Pegasus in the dying days of the Three Tribes Era, Cirrus was cast out and left to die when she refused to follow what other Pegasi did in all walks of life.
 
Left to die, she would have, if not for the love and compassion of two other ponies who like her had been outcast by their own kind for refusing to follow what others thought and did.
 
Brought together at last by a figure they only call Cosmos, Cirrus, Twilight, and Lilly would find in each other the lo the love and acceptence they had longed for.
 
It would be this love, and the powers bestowed on them by the Prime Magic itself, that would help to lead Equestria through its darkest times.
 

 
Like her sisters, Cirrus has an unrivaled command over her chosen element. Her mastery of Pegasus magic is unmatched across Equestria.
 
Alone, Princess Cirrus is a one mare army. But when the Trinity stands united, there is nothing on Equus that can stand against them.
 
There is only one power they fear. The very power that brought them together long ago,though that same power has not been seen for an age or more now.
 

 
Just a bit of backstory I made after I bought the character. We will meet the other two in time.