
Burst Mage · magic (AP) damage
Orianna is a Burst Mage that deals magic (AP) damage and brings airborne. Some of their lockdown (airborne) ignores tenacity, so you dodge it; you can't cleanse or Merc' through it. Below is Orianna's highest-win-rate build from high-elo games; open the counter-build tool to tune it against your specific enemy team.

Orianna's Attacks deal additional magic damage. This damage increases the more Orianna Attacks the same target.

Orianna commands her Ball to fire toward a target location, dealing magic damage to targets along the way (deals less damage to subsequent targets). Her Ball remains at the target location after.

Orianna commands her Ball to release a pulse of energy, dealing magic damage around it. This leaves a field behind that speeds up allies and slows enemies.

Orianna commands her Ball to attach to an allied champion, Shielding them and dealing magic damage to any enemies it passes through on the way. Additionally, the Ball grants additional Armor and Magic Resist to the champion it is attached to.

Orianna commands her Ball to unleash a shockwave, dealing magic damage and launching nearby enemies towards the Ball after a short delay.
R Command: ShockwaveHover a crowd-control type to see which ability it comes from.
Sorcery
Summon Aery
Arcane Comet
Deathfire Touch
Axiom Arcanist
Manaflow Band
Nimbus Cloak
Transcendence
Celerity
Absolute Focus
Scorch
Waterwalking
Gathering Storm
Precision
Press the Attack
Lethal Tempo
Fleet Footwork
Conqueror
Absorb Life
Triumph
Presence of Mind
Legend: Alacrity
Legend: Haste
Legend: Bloodline
Coup de Grace
Cut Down
Last Stand

Based on 5211 games · 46.9% win rate · challenger+grandmaster+master+emerald-diamond+platinum-emerald · patch 16.18.1.
Sorcery
Summon Aery
Arcane Comet
Deathfire Touch
Axiom Arcanist
Manaflow Band
Nimbus Cloak
Transcendence
Celerity
Absolute Focus
Scorch
Waterwalking
Gathering Storm
Resolve
Grasp of the Undying
Aftershock
Guardian
Demolish
Font of Life
Shield Bash
Conditioning
Second Wind
Bone Plating
Overgrowth
Revitalize
Unflinching

Based on 133 games · 29.3% win rate · challenger+grandmaster+master+emerald-diamond+platinum-emerald · patch 16.18.1.
Sorcery
Summon Aery
Arcane Comet
Deathfire Touch
Axiom Arcanist
Manaflow Band
Nimbus Cloak
Transcendence
Celerity
Absolute Focus
Scorch
Waterwalking
Gathering Storm
Inspiration
Glacial Augment
Unsealed Spellbook
First Strike
Hextech Flashtraption
Magical Footwear
Cash Back
Triple Tonic
Time Warp Tonic
Biscuit Delivery
Cosmic Insight
Approach Velocity
Jack Of All Trades

Based on 69 games · 53.6% win rate · challenger+grandmaster+master+emerald-diamond+platinum-emerald · patch 16.18.1.
Sorcery
Summon Aery
Arcane Comet
Deathfire Touch
Axiom Arcanist
Manaflow Band
Nimbus Cloak
Transcendence
Celerity
Absolute Focus
Scorch
Waterwalking
Gathering Storm
Resolve
Grasp of the Undying
Aftershock
Guardian
Demolish
Font of Life
Shield Bash
Conditioning
Second Wind
Bone Plating
Overgrowth
Revitalize
Unflinching

Based on 64 games · 42.2% win rate · challenger+grandmaster+master+emerald-diamond+platinum-emerald · patch 16.18.1.