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.
Rammus's biggest downfall is that he has poor magic resistance, and taking the time to stack magic resitance in game minimizes the damage that rammus can do in game. The goal of this guide is to maximize the amount of damage that rammus takes endgame, while also maximizing the damage output of rammus.
The shoes can be replaceable with merc treads if the opposing team is all casters, or focuses on CC. The item sequence is built so that way you always go Armor>Health>Armor>Health.
To initiate fights powerball in, go to your defensive curl right away, taunt your focus, and then pop your ult. Then use your exhaust on whichever hero is either an autoattacker, or is the second target.