-and why did you buy him/her?
Was it because the champion was overpowered? Underpowered? Badass looking? Cute? Did you buy that champion because he/she was a demacian or from the void? Is it because the champion was a yordle? Is the champion your ace in the hole to victory? Your lucky 8-Ball? Do you feel badass using that champion, reguardless of if you win or lose? Tell us why you main the champion you chose why don't 'cha?
I main Kha'Zix because he's a melee creature from the Void, and I LOVE void champions. On top of that, I love his voice and quotes, and his Mecha Kha'Zix skin reminds me an awful lot of the Promethean Knights from Halo 4. I fell in love with the champion before I even got to play him.
Ahri, I bought because of her design (again), and started out by playing her as a Bot lane before playing her as one of my mids.