Chapter 1
First guide here on Mobafire so rate and tell me what you think!
To start off, I would like to tell you alternate ways of playing as Soraka. My ABSOLUTE FAVORITE way of playing Soraka is a more offensive Soraka. ( Which does take a different build than I posted ) Another great way is how I built on this guide, Tank Support.
Items
Along with the Runes for Soraka, there is some diversity to what people use for items. I prefer to start with a Dorans Ring. 
Doran's Ring gives you the Mana Regen you need to stay in a lane longer. It also give additional Health to keep you from being too terribly squishy and Ability Power to keep your partner up easier :) I also get a second Doran's Ring and 
Ionian Boots of Lucidity on my first trip back to the base. I prefer the Ionian Boots of Lucidity because the Cooldown Reduction is AMAZING for Sorakas heal ( which has a very long cooldown ) I also find myself debating on if I should get my Morellos Evil Tome or 
Spirit Visage. 
Morello's Evil Tome provides the Ability Power, Mana Regen, and Cooldown Reduction needed as a good support. But the Spirit Visage passive is very nice for any healer. Additional healing to yourself in dirty situations is a VERY helpful and sometimes essential thing. Next I get Aegis of the Leagion because the Health, Magic Resistance and the Armor being an aura is a GREAT support item. Giving your team the buff while also keeping you less squishy is a very nice thing in a team fight. Next is Shureyla's Reverie because Mana and Health Regen is very nice and the base Health helps alot to keep you alive. The Active is also very very nice to get away from those hard to see ganks and such. Next you can either get 
Zhonya's Hourglass or 
Abyssal Scepter depending if the other team is composed of more Attack Damage or Ability Power champions. And if it seems too even to tell, then pick depending on which champion on there team has more kills and who seems to be a better player. The Abyssal Scepter gives the Magic Resistance needed to be more survivable against AP Champions and as always, the must needed Ability Power. The Passive is also very nice for your team mates who seem to have troubles getting through that Magic Resistance. Zhonya's Hourglass is a must have ending item as Soraka. Near the end of the round, people have started to figure out that if Soraka is alive... so is her team. You end up getting targeted by nearly everyone all the time. So, when they decide to target you, you click the Active and BOOM no damage and usually, they havent targeted another person yet while you are taking no damage and your team is utterly smacking them left and right. It also give the Armor to keep a squishy alive and again, the Ability Power.
Masteries
Masteries for Soraka are pretty simple and relatively easy to figure out. Even though the MP/Health Regen sounds nice... the amount it gives you is infintismal.
Team Work
Soraka is GREAT for team fights when pushing hard down that mid lane for several reasons. Soraka has a great heal that end game isnt too long of a cooldown. She also has her AoE heal the heals every champion on your team for quick get away heals or the OH **** button heal to save a gank or someone across the map who is tower diving and would otherwise not quite get away. She also has her Infuse, which gives mana to you and your teammate. It also will silence the enemy target and do a considerable amount of damage. For that reason, Soraka can be a great harraser. Soraka also, on a lesser note, has her AoE damage ability. It isnt very helpful but in team fights can be the difference of someone getting away due to its good range.
Farming
Farming as Soraka is VERY VERY easy. You have a Heal, something to give you mana back, and of course, your AoE hit. It hits all enemies around you with a relatively low cooldown. So spamming this ability is pretty easy with 2-3 hits to kill an entire group of minions that would otherwise take a AD melee champ 20-30 seconds to kill... you just did it in 5-8seconds.
Pros / Cons
Soraka doesnt have very many cons to be honest. Soraka is VERY squishy at beginning of the game but thats about it. Her Pro's are very high though. Soraka has a Heal, which also heals for a good amount and gives armor for a certain duration to the healed target. She also has her Infuse which is great for laning longer and can harass very well with it for no mana cost. Also she has her AoE damage that costs low mana and has low cooldown. Sorakas Ultimate ability is AMAZING and there is no other spell like it on League of Legends. 
Wish, Sorakas ultimate ability, heals every champion on your team for a considerable amount. Upon that it is instant cast and doesnt have a super long cooldown. All in all, Soraka is a very nice champion to have on your team and I LOVE playing her.
PROS
Great farmer
Great harrasser
Multiple heals
Can deal damage while supporting team
CONS
Squishy
Targeted ALOT
Runes
As for Runes, you can pick and choose from what I have there, but I have taken into account that AP Quintessences might be a better choice but I am still in favor of the CDR.
Unique Skills
This build has survivabilty over most other Soraka builds. I've taken the liberty to compare my build with others and most of them are either AP builds or mixed AP Support builds. The top rated build on Mobafire as of RIGHT now (Nov 9, 2011) is AP Soraka. I can see why as I tried the build myself in game. I did great and I was taking on Tryndamere without a worry in the world. BUT, I could not support for ****! Why? Because, that build has NO COOLDOWN REDUCTION WHAT SO EVER! You can get the Ionian Boots of Lucidity to get a little more with it but you just dont have the cooldowns to keep heals going for long before people die and get angry with you for not supporting as a support champ. Simple enough... my build is much better for Ranked ( IMO ) and for REAL supporting.
Situational
For items, the situation is what calls for the timing. As for the Zhonya's Hourglass and Abyssal Scepter it kind of depends on the opposing teams composition. If they are heavy AD then I suggest getting it earlier into the game. And the same goes for the Abyssal Scepter but for AP.
Build Guide
Discussion (2)
