Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This build is usually able to do 200k+ damage per round. It's best used against melee teams. Depending how the opposing team builds, you might want to switch the boots and hextech for magic pen items.
Breakdown of each item:
Rod of Ages - This item is a -must- for any Cho. Get the Blasting Wand first so you can have increased damage. The AP here is essential for your Vorpal Spikes and your Feast.
Boots of Swiftness - You can use either this or Boots of Mobility. While you may be a tank, you need to be able to move around fast. The other items will make up for any ability you might gain from the use of other boots.
Thornmail - Perfect against melee teams (provided they use basic attack). If you're -not- getting the most damage from basic attack, switch it for another item. I'd recommend Force of Nature or Randuin's Omen (for the AOE armor debuff).
Rylai's Crystal Sceptor - Another must have for use with your Vorpal Spikes. Anything they hit will slow down your target, plus you'll get more AP.
Hextech Gunblade - If you make it this far, it's essential to focus on damage more than defense. You'll get lifesteal, more AP and a throwable weapon. Far too many times has that last bit been useful for me not to include it.
Sunfire Cape - Again, this is for use against melee teams. You'll get extra armor and it'll burn any nearby opponents.