This guide depends on your skills to defend your allies and support them in team fights. You should be the one who takes damage and deal damage. Rammus is a late gamer so u shouldnt be going in team fight in early game. But if you can survive until 20-25 min then its time for you to show up in game. and if game goes to 40-60 min you are the ultimate defense of the team. And also you will be that strong that you could go ahead 5v1 in order to save an allie. In late game going 5v1 wont bother you becous no one could get you that easy with w opened. after saving allies you can easily use q and get away quickly. Most of time teammate like ''i luv u rammus <3 '' and kinda . So i prefer him as the ultimate one hopu u find it usefull :)

Runes are nothing but early game help (except quintessence). I preffer armor seals for early game defense 2v2 or 1v1 it will be usefull. Also they gave a little damage but not that usefull. health marks they gave best health from runes so uyou need every hp to stand longer in team fights especially between 0-7 min. magic resist glyphs cuz u wont get much magic resist at early they are in a case u got 1 ap in ur lane. Finally quintessence for late game 3 health quintessence (total %4.5 healt) it will be good in late game cuz again u take a very little damage in late so u need every single hp to stand longer and grant your team kills.

masteris wouldnt help that much but anyway some will help out greatly. summoners wrath and summoners insight will help out you and your team with exhoust you wont let enemies run away or in tf get enemy easier.Others like health bonus or def bonus or magic resist but one is greatMercenary the one will grant you very usefull gold in late game and for that you would gladly leave kills to your team.

While writing couldnt remember the sequance clearly but i know the criticks. So first up you get W for defing turret or your allie. Secondly get E to take advantage of fighter take them to turret and get hit by turret. And also using E then quickly using W will damage your opponent more as if W hits magic damage for every hit you take so enemys health will go sown little by little but remember you dont have much health and armor at starting so dont forget to recall often. First up u should get W to lvl 5 as quick as possible but dont forget to upgrade ulti at 6,11,16 or it wont be good. secondly if hteres no ulti upgrade or W upgrade u should upgrade E lastly u should upgrade Q cuz its only for chasing up and stunning or else if you could interrupting enemy ulties ( warwick,katarina etc.).

This is the most importent part of game if your opponents are only ad then it will be easiest game u would get in cuz rammus's def will be too much that even turret will hit only 25 or smth. and also as his passive it will grant huge damage and u will be the ad carry (nearly :)) no w-one would get u on 1v1 on late game. Even maybe 2v1 or even 5v1 :D but dont get overconfident seriously :D
if your opponents are a regular team with ap's ad's jungler tank etc u should use the regular build thats i will start up writing first. if your opponents are full ap thant that game's probably yours cuz they are noob :D

So first up the general build :

first up get Boots of speed and 3 health pots it will be fine like that. Gether up Cloth Armor and after Ninja Tabi it will reduce any phisical atavk by %10 so its very usefull for a tank. After that u should get the second item Hearth of gold it should be gethered as quick as possible but after ninja tabi it will grant 5 gold every 10 sec so u would get great amount of gold in late game. But dont transfer it into Randuins omen it will be nearly one of the last items to get. After the Hearth of gold ypu should be able to get in litlle tf s and dont get hurt that much but dont get overconfident or it will go bad for you and your team.

You should check your opponents every minute for their items, powers etc. so build up under their condition. İf ap's are more powerfull so u should a-start up building up Bansheed Veil first starting up with Negatron Cloack then the health and mana and finishing up with veil itself. but never forget about the armor its the most important thing so get Sunfire Cape Starting up with Chain West then teh belt and finishing up with Cape itself. it will grant good health and armorr as the passive would help in tf's . But if the opponents ad and ap are nearly same or ad are better so get Sunfire Cape first then Banshees Veil. and it will be like this:
Ninja Tabi,Hearth of Gold,Sunfire Cape,Banshees Veil. so its the late game and there your powers and skills will grant kills to your team in tf's. its like 35-45 min of the game. So game could be over at by this time but if nor so continue up the build.

So we got 2 slots empty. As if its now likly 40 min u can starting to get Guardian Angel or if u think its ok to get Randiuns omen abut now Heart of gold gone but its already make out nice gold so you get randiuns with using hearth of gold. so u get 4 really worrth items for tank. and also all of then got really nice passives (you can read discriptions). so as 5th item you should get Guardian Angel for longer fifetime. and the last item actually will be by the way of your opponent if opponents are balanced between ap and ad u should get Aegis of Legion. if ad are more powerfull get up thornmail. if ap's are more powerfull then get Force of Nature . so its your build for standart games and you would figure it out in time how u should be going on rammus.

Thats in case opponents are all ad or all ap :
if all ad so then could never get u on 1v1 or even 5v1 but again dont get overconfident.
so for full ad opponent your build will be :
Ninja Tabi, Sunfire Cape, Thornmail(its not actually worth buying early in standart cuz it wont be helping if theres ap's), Frozen Mallet,(this 4 items will get rid of opponent very well so after this u can go a little ap tank so you could deal more damage to enemies or go a much greater tank) for more ap tank build continue up with Zhonya's Hourglass, Athenas Unholy Glory(for cooldown) OR Rylias Crystal Scapter(for more health)
and maybe after 4 items u wanna go much greater tank so you can go Randiuns Omen and Guardian angel

if the enemy is all ap:
Mercurys Treads,Banshees Veil,Force of Nature,Maw of Malmourtius,Randiuns Omen,Sunfire Cape(last two items for under turret and health)

This whole build should help you in gaem to get your teeam further in late game and to victory. Hope it will be helpfull for someone. And please leave comments :D

See ya in league :D