Ranged matchups: Lane sustain and diving tankiness.
Durability and crowd control
After immobilizing an enemy champion gain defenses and later deal a burst of adaptive damage around you.
After taking damage from an enemy champion, the next 3 spells or attacks you receive deal less damage.
After 10 minutes gain 8 Armor and 8 Magic Resist and increase your total Armor and Magic Resist by 5%.
Increase your Tenacity and Slow Resistance for each summoner spell on cooldown. Immediately after casting a Summoner Spell, gain a larger burst of Tenacity and Slow Resistance for a moderate duration.
+65 health and +10 AP or 6 AD, adaptive
Periodically your next ability used has its mana or energy cost refunded and restores some of your missing mana or energy.
Gain 3% extra MS. Gain extra AP or AD, based on your bonus MS, Adaptive.
Aftershock's massive addition of tankiness allows Ornn to dive into the enemy team during fights with [E] and absorb a ton of damage.
The bonus Armor and MR also empowers the damage of [E] if you're able to proc Aftershock with a Brittle auto or [R] first.
Bone Plating's early mitigation is great for absorbing early harass until you're able to get an item lead with your passive.
Conditioning's double bonus resists synergizes well with Orn''s [E] damage as well as role as a front-line tank.
Oppressive lanes: If you're playing into an incredibly oppressive lane (Teemo) Second Wind here will help you survive lane a lot more safely.
Unflinching allows you to stick to enemy champions for a Brittle auto in fight fights. Ornn is incredibly susceptible to being kited before he can get into position for an [E] knock-up.
Manaflow Band grants you the mana sustain you need to stay in lane as long as possible so that you're able to effectively use your passive and abuse item power-spikes.
Celerity's bonus Movement Speed grants you the bonus speed necessary to stick your target in fights and position for a well-placed [E] knock-up.
The bonus Movement Speed also help you get to lane quicker in tough matchups where you have to recall often.