Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Threats to Orianna with this build
|Karthus||Karthus will have trouble damaging you, whereas you can deal a ton to him. With your protect, his ultimate isn't as meaningful.|
Start out with a dark seal and health potions so you can build Mejai's. If you feel concerned with your lane opponent, take Doran's ring. Go for your long range poke but don't use up too much mana.
Middle to late game
With your ability power up, your dissonance is a force to be reckoned with. Keep up the poke, try to place your ultimate on a few enemies at once. Always target carries so you can blow them up in a few hits.