Arcane Comet

Effect

Passive: Dealing ability damage or pet damage to an enemy champion hurls an Arcane Comet at their current location that lands after 0.8, dealing 15 to 110 (+ 10% bonus AD) (+ 5% AP) of either physical or magic damage to enemies within a 140 radius upon impact. This damage is increased by 0 to 100 by 5, up to a maximum of 30 to 220 (+ 20% bonus AD) (+ 10% AP) at maximum range.

Variable Damage: This effect deals either physical or magic damage depending on the damage contribution from your attack damage and ability power to the effect's damage formula.
Greater bonus damage from the AD ratio → Physical damage
Greater bonus damage from the AP ratio → Magic damageIf the damage contribution of AD and AP are zero or otherwise equal, the damage type defaults to magic damage.