This is strictly a main tank build. This build is designed for initiation and in your face harassment. The damage from this build comes from the simple fact of being able to hit your enemy with out having to stop, ever. Its primarily designed for a solo lane and becoming an immovable object that the enemy has no choice but to deal with.

I use magic resist, armor, attack speed and movement speed runes. Now I understand most people wont use attack speed runes but early game it really helps with vorple spikes. This translates into more hp and mana regained from passive and more aoe dmg vs your lane.

I use a complete defensive tree build. This works really well with passive. You lose less health while gaining a lot. This allows you to stay at full health and giving you infinite lane presences. Most people do not use the bonus xp mastery but i feel that if you can out level a few people on their team it allows you to tank really well. Before you ask, no i do not use dodge runes or masteries, why? Cuz im mofuggin chogath, hit me all you want, ima get all my health back in a creep wave.

Now from my perspective of the game, ability power scales earlier in game than attack damage. So you dont need as much resistances for attack damage. This is why i start off with a force of nature. I make sure i dont get nuked down by ap carries and i regen the dmg taken from AD. FON also works really well with feast stacks. Second is merc treads, nothing pisses ChoGath off more than being cc'd, especially when he is hungry. Third item i go for is Randuin's Omen. Gives you a health boost as well as giving you the ability to become even tankier during a nuke. It also adds to the health regen. Those are the core items and from hear on out you want to counter build against your enemey. I listed some items that are really good for cho gath but at this point you can choose to go for more dmg or become even tankier.

I always start with vorpals unless my team is invading the nme jungle in which case you want rupture. Vorpals is really good for last hits and harassment against malee. 2nd you get rupture and finally silence. If there is alot of ap silence is best to primary. If there is alot of ad than you want rupture, but i always get vorpals maxed out before anything else.

I see flash on cho gath alot. If you need flash on chogath than you have no clue how to use your rupture and should go out and shoot yourself. Rupture gives you the ability to close distance. I usually run Exhaust and Ghost. Exhaust for the reduction in resistances and the slow. I use ghost for getting around a fight very quickly. The ideal situation is after you land a rupture you run up and silence, once in malee range you exhaust and you finish with the Feast.

I use this build for in your face tank action. I can be early to a fight and be the last one to leave. This gives my teammates the opportunity to choose when and where they want to enter the fight. It also allows you to enter a fight and if you teammates think its a bad fight you can pop rupture get out, regen and return for another go. If gives you a lot of play room when trying to work out a proper initiation. Don't take my word for it, try it out and watch the nme team try to kill you... its hilarious.