I don't know what exactly the introduction is utilized for. But I'll just go ahead and give you the rundown on Cho'Gath.
In case you didn't already know, Cho'Gath IS, or IS ONE OF, the best tanks in-game.
If you disagree, well then please, do use my build and see for yourself.

Disclaimer:
This build is intended for use by those who have a good understanding of every champion in-game, what their abilities are, and how to avoid them. This build WILL work against any champion and can even be used to solo a lane with two, in the event of a jungler.
In order for this build to be successful, you have to be the most aggressive critter out there, never backing up when you're getting hit. I'll explain more in detail soon.

All right, so why the mana regeneration runes?
Cho here is a very mana deprived champion early game, with the mana regeneration runes just constantly regenerating your mana, you can keep on pushing your lane forward without worry.
The regen from the runes also syncs pretty well with Cho's passive, regenerating a certain amount of mana every time you kill a minion.

I went with a 9/0/21, the 9 for the added damage with Cho's attacks and the 21 for the extra mana regen, and cooldown on your skills. The little extra CD reduction will help you a lot in the long run when you're using your Feast on little minions and champions.

Levels 1 - 8/10

Start off with a Regrowth Pendant and a Mana Potion. The pendant combined with your mana regeneration runes will allow you to stay in your lane for long periods of time without having to worry about running low on anything. The Mana pot is used as a reserve in the event that there's an attempted gank and you need to push back out asap. Your main objective at this point early in the game is to be as agressive as possible, keep your opponents low on health, and push them as far back as possible, so as to starve them from exp and gold.

Levels 8/10 - 12/13

Once you head back, you should have enough gold for Boots of Swiftness and for a Ruby's Crystal.
You may even have enough for a Giant's belt.
Use the speed on these boots to escape ganks, and to chase down your opponents who may already be weak

Levels 12/13 - 18

At this point, you should begin to assess your enemy, look at what builds they're going for, and plan accordingly, see which piece of armor will help you a lot more, either go for your Thornmail if the carry on their team, or majority of their team is going AD, or go with Force of Nature if you notice them going with AP. Either way, I highly recommend getting both. Just make sure to assess first, see what piece of armor is more important at the moment.
After you've gotten both of those pieces, I would begin to work on your Guardian Angel.

This would really complete the build, though I go for Zhonya's Hourglass Just because it adds to your armor, and it gives you quite a nice AP boost in the end, adding to the AP that you lack.

I go with Flash to escape any ganks that I may encounter while laning in the early levels.

Clarity To keep my Mana going so that I can continuously spam my skills on enemy champions.

Here I'll give a detailed explanation on how you should play Cho'Gath with this build.

Here's the brief:
Be as aggressive as possible.
Never turn your back to an enemy you have weakened.
Make use of your Clarity as early game as possible.
If you run low on Mana, keep striking minions to get it back.
Make use of Cho's Passive, it'll help gain your mana and health back when its low.
Keep your enemy's health as low as possible.
Don't kill your enemy, it'll only give them opportunity to come back and harass you.
Let your minions attack the tower, don't touch it at all unless you deem it safe to do so.
Gain your six stacks of health ASAP.


At level 1, you'll want to start off with Rupture.
This will be your main way of escaping, and engaging enemies. It'll also be your primary aggressive attack when laning. You'll want to spam this and try to land it on whoever you're laning against to keep them back. As you add skill points into this, you'll notice just how much more damage it does. At level 5, this does quite a good amount of damage.

Harass your opponents as much as possible with Rupture and Feral Scream, never EVER chase after an opponent with low health, its best to keep them around with low health, this causes them to stay at their turret, doing whatever they can to protect it. If they try to push you back by auto attacking, dont move, keep attacking minions, ignore their attempts, and if ignoring doesn't work, then Rupture away and back off a bit.

At level 5/6 You should already be at their tower watching your minions chip away at their turret. LET THE MINIONS DO THE WORK Whatever you do, DO NOT touch that tower, simply watch your opponents as they try to last hit your minions for Gold, because at this point, you're starving them of gold and exp. Keep harassing them with Rupture whenever they try to get last hits on your minions.

9 minutes into the game, if you've played your cards right, opponent's tower should be out, or close to it. you should already have about two/three stacks of health, and should be working on warmog's armor.

Once their tower is out, commence to helping your teammates out with their towers. Using the same method you did on your lane.

In team fights, its essential you use your rupture and feral scream to disable your enemies as much as possible.
Dont be afraid to take a bite outta' a champ who's health pool is naturally low. Like Annie for example.
Once team fights have begun, remember to continue being as aggressive as possible, but at the same time, protect your team. Ward off any enemies trying to take out your weakest teammate.