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 for something you do not see very often but can be very effective. The summoner spells I use are Teleport because in combination with Powerball it can be very effective to reach any are of the map in a short amount of time. I use ignite for that extra bit of damage to finish off the enemy champ about to give you more gold. I use all armor and magic resist runes. Even though the Marks I use are all secondary runes they are strong secondary runes. Even in Searz's rune tips article he mentions these secondary marks for armor and magic resist to be strong anyway. If you would like to switch them out with Magic Penetration runes then feel free. I use these runes because even though you are going Ability Power with Rammus does not mean he can not use this extra survivability. As for the masteries I make sure to get the magic penetration mastery in the Offense branch which takes 9 points and use the other 21 to get the full Utility branch.
I go with doran's ring to start off so that you can use your abilities more, you have the health boost, and you get some extra power behind them. You already have armor and MR runes so you should be fine without Doran's shield. Grab a Health pot if you want.
The boots come second and Sorceror's Shoes are going to give you the most bang for your buck in an AP Rammus.
Rylai's Crystal Scepter is going to give you more health, more AP, and cause people to be slowed by your abilties. Your ultimate is Area of Effect so slowing down enemy champs keeps them taking damage.
Glacial Shroud is perfect for giving Rammus some armor, some mana, and reduced cooldowns.
You have armor, you have health, you have mana, now Abyssal Scepter gives you some Magic Resist and lowers enemy magic resist. This works great with Rammus because Rammus' abilities all have to do with being up close. Meaning anyone taking damage from one of his abilities is going to be close enough to have their Magic Resist reduced.
Now is the time for some extra firepower and that will come in the shape of Archangel's Staff. It will give you some much needed AP and mana regeneration.
At this point upgrading Frozen Heart would be a good idea as it will slow down DPS champs trying to kill you, give you even more cooldown reducation, more armor, and more mana.
Finally you should buy Banshee's veil for extra health, mana, and survivability.
ANY QUESTIONS OR COMMENTS PLEASE POST. IF YOU USE THE BUILD RATE IT AFTERWARDS!