Hello! This is my first build on mobafire, so be gentle mates. :) Also, I am not a native english speaker, so sorry for any misspellings. For some time I've been playing swain, watching others do, try out different builds and overall face pound. This build is my conclusion and in my opinion, the best way to play this swell character.

Ok, so let's start with some pros and cons.

Pros:
- Awesome character overall
- Nice zone of control
- Can 1vs3 if played right
- Deals crazy amount of damage
- Is the one of two mages (other is vlad) who can take a beating and still wind up victorious
- Having a Big Bird in team makes you win! XD
- Has a nice, russian officer feeling
- Nothing beats pushing mid with CCCP anthem playing in background
Cons:
- Slow
- Hard to master
- Extremaly mana needy

Here stuff is kept simple:
Vitality runes give you a bit more hardiness. You are not a tank, and it helps survive early game.
AP runes and quints - I like to start off with a bit more AP - with Doran it's 39, which is a decent start
Magic Pen - simply a waste to have other reds on a mage
If you want to counter mana issues, you can drop the blues for it or put in one mana reg quaint, but I don't advice that, which I will explain later on.

Masteries are pretty standard and I don't think they need to be explained.
Summoner spells:
Ignite and flash are by far best compilation - flash to close the distance (you are slow, remeber) and jump in to throw a W in their unsuspecting faces. Ignite is pretty self explanatory - 20% more dmg from Torment makes a deadly combination.
Viable one is also teleport in place of flash.
I do not reccomend clarity, as skipping ignite is very harmful if you play against, for example another Swain or Vlad. Also, without flash it's hard to chase or run, so... Skip it. Others are not even worthy of your Noxian Attention. **** Demacia.

Start of with Doran - mana reg, additional hp for surrvival and AP, perfect deal for 475. Keep harrasing mid (You are THE MID. **** others. Using this build, I defended mid against anyone, including teemo, mordekaiser, soraka, katarina, **** like that. None stood a chance against the Crowman.) until you get around 1300 - buy hextech( or, if you prefere to be full ap - catalyst of the protector) and two mana pots. GO and get blue buff (pots will help you maintain mana to kill golem) and if you have a jungler, resolve it with him, by ordering (Yes, you can order, you look like a Russian officer, damnit!) to take their blue. Or just destroy their jungler(Best way. Gold plus buff). Not really important how you get it, but you must have it. No blue=less pwng, especialy early game. Next pick regular shoes, after it Rod - more mana, life and AP. Next, finish your boots. By the time I have boots I rarely play anymore - enemy usually dies out on me. If you do - adjust to the situation. Lots of Magic Res? Get Void Staff. No magic res? Rabadon + Zhonya and Abyssal. Sell doran, if you lack slots or some gold after finishing boots.

Survival items and you: why not.
I do not pick things like Rylai, I simply have no need. If you have Hextech and Rod, Archangel is neat too, you heal like a Boss. You deal damage like a boss. You slow like a boss with decripify. You need to slow more? Get a red buff from the Raven-bitten carracas of your enemies. It's better to pack moe AP than HP. More AP equals more spell vamp from Ult.

Drop a W down their legs, followed by E, then Q, while popping ult. Timming is really important - sometimes, when you play against chars like Kennen, who stun like hell, it's a good idea to pop Ult earlier, to ensure heal after the stun ends.
Alas, you must always make sure to have E on thier faces - 20% more damage can devour their ***es in seconds. If you can maintain a good rotation, you don't even see squishies like teemo die, only noticing the Heal Juggers like Mundo dropping dead.

Nevermove: How to
The important thing here is practice - you can't land good nevermove without few early mistakes. What I learned is that a very good idea is to place it so that enemy is in the center - it allows you to trap him or make him lose something important, like Flash or popping Ghost in terror. Then continue with the eating. Also, it's good to know how you can land it - nevermove can be landed good around half the circle range from the spell cast range. Make sure to watch your enemies keenely - people tend to move in patterns. If you learn it - they are your prey.

Why mid?
Simply. Good Swain is the most annoying harrasser in the game - you can easily keep any enemy under half health. Also, if you face some strong harrasser yourself, just turtle till you reach 6, when you can have All-You-Can-Heal-Buffet. Also, with flash, ignite, nevermove and torment you can get a first blood as far as lvl 2. It's a simple trick, but often works.

Why nevermove lvl 2?
Some people take nevermove on lvl 1. That's ******ed. Lots of cooldown and no harrassement. Pick torment and drop it on that Ashe now and then to have her nice and tender for deep ****ing lvl 2-4. Nevermove lvl 2 allows you to control your lane better - people get frisky when you hit them in the face with it, they try to move carefuly and that's how patterns are made, and they are, of course, your friends. Also, it's better to farm than Q early on.

Monster buffs:
Get them. You need blue for mana. I usually go at lvl 6-7 for mine, thanks to Swain's amazing passive, that gives you mana when you last hit. Nicely planted W gives you gold and a buttload of mana.

Playing safe:
If there is a jungler, ward the sides. Sometimes it's best to wait a while in the bushes before enclosing on your pray, it prevents counter-gank. You can easily turret dive, thanks to Flash+R but make sure they don't have Exhaust or long stuns, otherwise you may die. Wait in hiding, watch your target and W them in the face, when they are in the right place. Cast E, then Q and ult. Sometimes feint advancing towards the enemy, so he will try to run form your W, that will not happen. Kill. Devour. Destroy. Don't be a Swain. Be a Swine!