Orianna is a very good champion that can be used in any kind of game. She can be used as carry, assasin,...
In this build, she is a very good mage with lots of ability power, which makes here extremely hard to beat.

I've chosen some runes to make her have a gigantic cooldown. The cooldown of her spells are also increased by the boots and by the Frozen Hart.

The Quintessences give her a lot of speed, to follow other champions and finish them.

She will have an enormous amount of mana and mana regeneration, which will help her a lot in early game.

The Items give her:

- COOLDOWN: With her cooldown, she can use her spells very fast
- ABILITY POWER: With her ability power, she will inflict massive damage

I gave her Ghost and Flash, because she will have a extreme high speed, which will make her harder to defeat or will be harder to run away from.