As you can see there are 5 swains listed above. The multiple Swain forms goes in this order:
Rammus Swain -> Vladimir Swain -> Jungle KS Swain -> Backdoor Swain -> Sentry Swain

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Rammus Swain Description:
You are now playing as Rammus, but only as Swain. You need hardcore defense and high health. Rammus Swain has been proven to tank better than Rammus' defensive curl with the same item build.

Item Build:
Boots of Mobility -> 3 Thornmail -> 2 Heart of Gold -> Replace Heart of Golds with 2 Warmogs

Skill Sequence:
Get Swain's W skill only, the rest are useless.

Battle Plan:
Okay now that you have all the items you're wondering "What the hell do I do?!" Don't worry, your battle plan is to let your squishiest ally hero lure and initiate. Your job is to go in when your ally dies and feeds and pop your W skill then pop ghost into the closest lizard spawn and recall. This works best if your team is below 50% health. Think of it as you power balling back to safety. If you didn't know, Rammus Swain has a taunt, but it requires the summoner to talk smack in all chat until the opposing team ganks you first. (Only suggested if you plan on initiating first with Rammus Swain).

Screenshot:
As you can see in the screenshot below, I out tanked a Vlad and had him rage at me.______________________________________________________________________________________________

Vladimir Swain Description:
Ever wanted to life steal as much as Vlad except with Swain? Well now you can with this pro build.

Item Sequence:
2 Ninja Tabis (For the skill vamp) -> 3 Spirit Visages (For the cool down reductions in between each bird shot by your ulti) -> 1 Oracles (For that ******** Twitch)

Skill Sequence:
You're building as a Vladimir Swain, so you'll only need your "R" skill.

Battle Plan:
When at a team fight and no one is initiating, you will now become the initiator. Quickly flash into the mob, pop your ulti, and then run back out then use heal. This will allow you to heal back whatever health you have lost from being targeted first. Run back in and within a good 4 seconds of chasing your opposing team will be dead.

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Jungle KS Swain Description:
Now you may think that the "jungle KS" in this Swain's build's title means to KS the opposing end's jungle. Wrong. Jungle KS Swain is a sure fire way to get you golem and/or lizard whenever you want. The build for this Swain will focus purely on movement speed so you can get from jungle to jungle faster.

Item Sequence:
Boots of Speed -> x6 Boots of Mobility (For a total movement speed of 9001)

Skill Sequence:
Decryptify -> Decryptify -> Decryptify -> Decryptify -> Decryptify -> Decryptify (You only require this skill so that you can fire it off on random mobs to pretend you are actually doing something)

Battle Plan:
This build is only suggested if there is currently a jungler on your team during the hero picking session. What you do is pretend that you're helping your teammate from getting ganked and when they activate their smite, you use it RIGHT before their golem/lizard dies. Now this here comes the tricky part. Be prepared to receive some "Omg wth dude?" or "wow rly?". Don't be alarmed, all you need to do is apologize and say "Oh sorry I thought the (insert hero name here) was going to smite it." If all goes well then your teammate will reply "Oh it's okay." You continue this until you have an inventory full of Boots of Mobility. Don't worry if you die to jungle/ganks, you have revive.

Alternative way of KSing:
Replace your summoner skill "Revive" with "Teleport". Now when the game starts you get your boots and a ward (if your jungler hasn't already gotten one) and you place it on their creep spawn. Recall, wait until the golem/lizard is at half health, teleport on that ward then smite it right away. This will create confusion and hopefully you will be excused. If your teammate happens to get angry, fear not for you will have gained the golem's experience and that's all that matters.

Tip:
You will only achieve 9001 movement speed if you have the full rune page provided in the build.
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Backdoor Swain Description:
Backdoor Swain is exactly what it sounds like. BD Swain focuses more on attack damage rather than speed, but speed is not to be forgotten. The purpose of this build is to backdoor your enemy's base and win ASAP.

Item Sequence:
Brawler's Gloves -> Zeal -> Boots of Mobility -> BF Sword -> Phantom Dancer -> 3 more BF Swords -> Convert all BF Swords into Madreds since the passive stacks and is definitely not a unique.

Skill Sequence:
You have the most skills just by playing BD Swain so you don't require any. Save all your skill points till level 18 for your Decryptify.

Battle Plan:
While your team is defending from your opponents' push. Use your clairvoyance to see if there are any minions guarding your target tower, if the coast is clear then use your ghost and quickly rush over there and down it. If you are successful then your opponents will think twice before trying to push again, ever.

Screenshot:
As you can see below I was able to get a positive KDR by kill stealing my teammates early game to farm up for my BF Swords.

Tip:
If you have the full rune page I have added above then you will be able to evade every single one of the tower's shots and it'll allow you to BD some more.
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Sentry Swain: Coming soon.

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Updates:
01/10/11 - *ADDED* Jungle Swain build
01/10/11 - *ADDED* Backdoor Swain