Hp5 Ornn Top

Ornn has one of the highest Base Health Regeneration stats in the game. Tied for 4th at level 18, not counting non-mana champions.

Start with what you're most comfortable with, but I personally prefer Rush Then build straight into Finish When you hit level 11 will upgrade into

With just these two items you'll have +450% Hp5

At level 11 Ornn has 16.9 bHp5

450% of 16.9 is 76.05 16.9 + 76.05 = 92.95 health per 5 seconds.

You'll also have plenty of mana regeneration (Mp5), 20% CDR, a Cleanse / 2 second slow immunity (if you use it properly), +30% Heal and Shield Power, and a massive AOE heal (Heal Power tripled) / true damage ability.

Further, you can also buy another Redemption, which will give another +200% Hp5, +150% Mp5, another 10% CDR, +10% Heal and Shield Power, .. It does not give an additional use of the active.

OR

You could always build other items. Of course, you still get another Ornn upgrade with his passive. Building for more sustain or going full tank from here would be fine depending on your preference.

You'll basically have Garen's passive but it doesn't fall off when you're in combat, making it impossible to force you to leave a lane. This works great as a split pusher. Alternatively, he would be incredibly useful joining his team for fights around objectives.

I think Runes are really a matter of preference here. Being a sustain build, Resolve is the most obvious choice. With Ornn's passive giving bonus resistances and crowd control kit, Aftershock may be better. This build will likely lead to extended fights and bonus "Heal Power, so Grasp of the Undying would be effective in restoring and stacking health. This could even be played as a support with Guardian, but your budget and shared exp will cause you to scale slower. The good thing about this is you virtually never need to leave lane, so you can get solo gold and exp while the carry backs.

Conqueror is obviously a good option, .. since it's good on virtually everyone ..

You might also consider some combination of Domination / Inspiration. I don't really think any of the keystones are great for this, but Domination will help to compensate for his lack of offensive stats. Inspiration helps to make efficient use of his utility. Two runes in particular catch my eye with this combination though. Cosmic Insight and Ingenious hunter can reduce active cooldowns by up to 45%. Since Redemption and Salvation have a 120s active cooldown, this would be lowered to 66s. That's one use roughly every other minion waves.