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.
Use this build if at least 3/5 of your opposition are magic users. This seems to consistently come out on top (if not near it) for most damage dealt and taken.
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.
Force of Nature - A perfect item for Cho. Health regen and magic resist all in one bundle.
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.
Randuin's Omen - Used mostly for the cooldown reduction and extra armor. If you can get close enough, it's also useful for the armor debuff.
Spirit Visage - Another useful Cho item against magic users. Depending on your opponents, this can be swapped for anything more useful.