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.
Introducing Rammus, the most over-powered hero in the League of Legends.
Rammus is a very versatile tank. His Passive Spiked Shell converts 25% of his armour into attack damage. With Powerball he can escape and gank with speed, and provide his team with the support they need to chase and survive. Defensive Ball Curl protects you from incoming damage, for example Karthus's ultimate, by increasing your Armour and Magic Resistance, but also returns damage to attacking units for a certain percentage of your armour as magic damage. Puncturing Taunt is the most useful ability Rammus has, it forces your enemy to attack you and when this skill is maxed, it is very dangerous. When your tower is under attack, you can use Puncturing Taunt with Defensive Ball Curl to output some major damage, and because they are attacking you, your tower also attacks them. Tremours is a pretty good ultimate ability that deals damage to units surrounding Rammus, allowing you to wipe out towers and minion waves fast.
I believe these runes are the best for Rammus.
Greater Mark of Insight - Magic Penetration provides you with stronger abilities.
Greater Seal of Resilience - Provides you with armour and increases until level 18.
Greater Glyph of Warding - This provides a bit more survivability against AP heroes, as they can be very annoying early game.
Greater Quintessence of Resilience - More armour = More damage.
I choose to go 9/21/0 for masteries. In offense I go for ability power and cooldown reduction, while grabbing burning embers which increases your ability power when ignite is used.
In defense I go for magic resistance and hardiness, following on into Harden Skin. I also grab dodge chance, increased health, increased attack speed and ability power, and Tenacity which decreases all damage dealt by 4%.
I start out with a Cloth Armour, two health potions and two mana potions. This allows you to health if you nearly get ganked early game or continue laning instead of recalling. I then go for Boots of Swiftness for movement and harrasing, Boots of Swiftness allows you to move faster around the map, gank, and chase. Thornmail is a must have with Rammus, this is because it increases his armour, attack damage and the damage returned stacks on top of Defensive Ball Curl. Sunfire cape is another great item, it gives you health, armour, attack damage, and deals magic damage to surrounding units. I usually avoid getting items like Frozen Heart or Randuin's Omen because it decreases enemies attack speed - Yes, you're thinking, isn't that a good thing? Nope it's not. That's because if you're versus a heavily attack damage hero for example Master Yi then you want him to attack you as fast as he can. He will be dealing more damage to himself then he is dealing to you because of Defensive Ball Curl, Thornmail, and Puncturing Taunt. The only reason I grab Frozen Heart is because it provides you with a high amount of armour, some mana, and cooldown reduction (Also slows attackers). Force of Nature gives magic resist, and great health regeneration. Finally, Aegis of Legion, this gives armour, magic resistance, and attack damage to you (Also gives health to Rammus) and surrounding allies (Aura).
I get Powerball first because it's easier to gank with at level 1 rather than Puncturing Taunt. At level 2 I get Defensive Ball Curl which helps keep your health up in tight situations early game. From now on you want to max out you Puncturing Taunt, this is because it is the skill that will carry your team to victory. When your taunt gets to 4 seconds long, you can drag enemy heroes from the safety of their team, to your team to take them down. When you cannot learn your taunt, then you want to go for Defensive Ball Curl. Grab your ultimae whenever you can, and when your taunt and defensive curl are maxed, continue on with maxing out Powerball.
Ignite is great to have to garauntee a kill, especially if blowing all your abilities doesn't kill them first time around. Flash is a MUST with Rammus, this is because when escaping you need something to make a distance between you and your pursuerm so flash is perfect for this. Also a side note - Using flash while in Powerball does not cancel out Powerball, so you can flash across minion waves if they get in your way.
Engaging the Enemy
When going to engage an enemy, it's best to first spend a second to prepare - Make sure all your abilities are not on cooldown, and if you have summoner abilities then that will be better.
Best way to engage:
Sit in the brush, and activate Powerball, wait for Powerball to gain some speed, then move towards your target. By waiting for your Powerball to gain speed means that your enemy has no time to run, once you hit them, they are all yours.
After your enemy has been slowed by Powerball, activate your Puncturing Taunt, and they will start attacking you and will follow you if you move.
Activate Defensive Ball Curl, and Tremours to maximise damage output, making sure you are also attacking them.
If by now you have not killed them, then finish them with Ignite.
Farming is not particularly easy with Rammus early game, but he can farm some decent amount of gold late game. If you need some money, Powerball past a incoming enemy minion wave and let your creeps deal with that wave, and head to the next wave. When you hit the next wave you will see two groups of three creeps, stand in the middle of them and activate Defensive Ball Curl, the minions will damage themselves, and if you have Thornmail, then you do this very quickly. I would advise that you do this only once every now and then, and never wait for another wave to come otherwise you could get ganked. You can increase the damage you do to minions by activating your Defensive Ball Curl.
In conclusion, Rammus is one of the best tanks in the game, this build doesn't give you much health, but you won't need it as they won't be able to penetrate your Armour and Magic Resist. Rammus can destroy people 1v1, 1v2, or even 1v3. To stay safe as Rammus you have to size up your enemies first. Pure attack damage heroes like Master Yi, Sivir, Warwick or even Pantheon can be harmless to Rammus because of his high armour. Heroes you will have to watch out for would be Malzahar, Doctor Mundo, and mainly AP heroes.
Thanks for reading my guide, and goodluck smashing with Rammus.