As with all League champions, specific items are going to be more effective depending on the situation. But there are certain items that are effective on Ornn in all games. These core items are going to ensure that you have the best possible experience with this champion.
Grasp of the Undying: This rune is one of the best for tanks. It scales with maximum health, making it effective for the entire duration of the game. One of the best aspects of it is that it grants you health as you proc it, making it especially efficient against melee champions which you can proc it often.
Demolish: Demolish is a great rune to take down towers fast. As Ornn, your kit doesn’t do anything to towers so having this rune is a must if you want to be able to push quickly. It allows you to take early tower plates for a huge gold inflow.
Bone Plating: This is a pretty basic rune to grant you more tankiness early on. While you will have a lot of health, armor, and magic resist as the game progresses, early on you are easily killable.
Overgrowth: This rune is one of the best scaling runes, especially if you can farm efficiently. It needs some time before you notice the effect, but overall it’s a great rune that will help you along the way during the entire game.
Biscuit Delivery: Biscuits offer extra lane sustain to ensure that you can recover from unfavorable trades. The extra mana granted by this rune allows you to spam your abilities more often as well.
Cosmic Insight: Cosmic Insight is an overall great rune, giving you additional cooldown reduction (CDR) to get your abilities back faster. The summoner spell CDR is really good as well, ensuring you have flash available more often and teleport to help your team.
Bonuses: +10-percent cooldown reduction, +6 armor, +6 armor
Starting items Doran’s Shield
Having extra health regeneration is crucial for every tank. Doran’s Shield grants you 80 bonus health to make you tankier early on and a great passive to help you last-hit with five extra attack damage against minions. This item is great early on but loses value as the game goes by.
During the farming phase, you are going to take damage from the enemy champions. Health potions heal back 150 health over 15 seconds and will give you extra time before having to back to base.
Core items Sunfire Cape
As the main core item of your build, Sunfire Cape helps you waveclear with ease and has a great teamfight effect, doing a lot of AoE damage when you use crowd control on opponents.
While Sunfire Cape is the core item of your build against AD-oriented champions, Abyssal Mask is the core against AP-oriented champions. Instead of the armor from Sunfire Cape, you get some magic resist, mana, and CDR.
Mercury’s Treads are the best defensive boots option available, especially if facing heavy-AP oriented compositions who have a lot of crowd control. It grants you valuable magic resist early on while you get going and reduces the duration of all crowd control—the perfect combination for Ornn.
But if you’re against teams with not a lot of crowd control, look to go for Ninja Tabi or Swiftness instead.