Greetings ladys and gentlemen,
I bring you: GALIO!

Huh? Galio? What is that?
Galio is a beast!

He can do great amounts of damage, tank pretty much everything, has a slow, a taunt a speed buff. HE IS UNSTOPPABLE.

I will show you the path of becoming this beast, join me and we shall defeat Noxus!

The power of the sentinel lies within the power of his believes.
You must not play Galio in this guide, you must BE Galio in order to play him!

So act like him, act like you were once just a golem, working for a man called Durand.
Durand made many golems, but he once had to stop making them for they were prohibited.
Though, Durand was a big boy, and he kept one golem anyway, the most powerful of them all: GALIO!

Durand was traveling around Runeterra in order to protect Demacia from hostile beings. Galio was supposed to protect the guy.
But, of course, Noxus ruins the party. They had send many assassins to murder Durand. Galio was heavy outnumbered and could not save Durand because of that.

Galio was broken, not physical, mental, because he failed at the one task he had to do in his life, protecting his master.
Out of nowhere, a Demacian girl comes by, and they looked at eachother.
They just looked, and then the Demacian girl walked back to her home.
This inspired and he looked up and thought: Right! I need to protect!

Thus he left for Demacia just like the girl, and afterwards joined the league of legends to protect Demacia from the evil Noxus for once and for all.

That was the past, and now we go to the present. YOU shall play Galio, you shall BE Galio, feel his sorrow and feel his urge for justice.

The sentinel has mysterious ways of doing what he needs to do.
Thus we must try to understand.
In order to know Galio, we must know his strengths and weaknesses.

Strengths:
+ You are a big *** gargoyle
+ You can tank anything!
+ You do great amounts of damage!
+ You have a slow, a speed boost, a special shield and a taunt!

Weaknesses:
- Your spells drain mana like a pinguin drains fish
- Your 2 main damage spells are skillshots, thus they require skill
- You are not full damage, thus not a real Ability Power carry
- Your initiate can be very slow at times, unless your flash is up of course.

Master these facts or else they will master YOU! And then, you have weaknesses exposed and that will be your undoing!

The abilities of this great sentinel should be understood. Thus I shall try to explain them for your tiny little brain (LOL JOKES, YKNOW I LOVE YOU).
Follow the way of the Galio:

Runic Skin
What is it?: Passive
Function: Defense motivator and damage bonus
This spell will get you 50% of your Magic Resistance as Ability Power. What does this mean? You can get a lot of Magic Resistance while having 0 Ability Power and still do a lot of damage.
Combining them brings ultimate destruction!

Resolute Smite
What is it?: Q - spell
Type: Skillshot (Circle)
Function: Main damage source and slow
Upgrade: 1, 3, 5, 7, 9
This is your main spell, especially early game you can do great pokes with it.
Keep in mind: This is a skillshot, meaning: it requires skill.
Try to predict the enemy's movement and then shoot!
It is okay to miss the first Resolute Smites, as long you learn from your enemy movements within the mid lane.

Bulwark
What is it?: W - spell
Type: Allied champion targetshot
Function: Defense boost and self-heal
Upgrade: 2, 8, 12, 14, 17
This spell will grant you a big *** shield which will boost your defense with a certain amount. If the target with the shield is hit, Galio get's health back. The heal will NEVER apply to your shielded ally. You can upgrade this spell either second, third, or balanced with the E - spell. Depending on the amounts of damage your enemy does midlane. The more damage, the more you would like to have this spell. You can make great combinations with this with both your passive (increasing the damage done) as your taunt (reducing the damage taken).
Keep in mind: You can also use this spell as a health regen only, for example when under attack by minions, this might save your life some times.
Keep in mind: The heal reduces each time! So the first heal will grant more hp than the last one.

Righteous Gust
What is it?: E - spell
Type: Skillshot (Direction)
Function: Speed buff and damage
Upgrade: 4, 10, 13, 15, 18
This spell can do nice damage in combination with your Q. Can also save your life or destroy the enemys life. The speed boost is very good noticable, they are leaves. If you follow the direction of the leaves (The direction you casted the spell) you will get a speed boost, the other way around does NOT work! The speedboost only applys on you and your allies, the enemys will only get damage from this spell.
Keep in mind: If you want to do more damage early game, upgrade this spell second, if not, upgrade it third/balanced.

Idol of Durand
What is it?: R - spell (ULTIMATE!!)
Type: Activation (Surrounding effect)
Function: Taunt and huge damage spell
Upgrade: 6, 11, 16
This is your main initiate. If you were to us this in the middle of the enemy team, taunting them all, will make you the best tank in the world. Combine this spell with W for more survivability and thornmail to do even more damage!
Beware though that this ability is already activated by just clicking on it, so a misclick can be fatal!
Keep in mind: Tenacity is this spell his nemesis. If they tend to walk out of your ultimate range, cancel the spell, this will make you still do a nice amount of damage.

In order to protect, we need more assistence, summoner spells!
There are a few options working for the almighty sentinel, namely these:


Main:
Flash
Type: Instant skillshot
Function: Moving a small distance instantly
Because Galio does not really have a spell to come in the middle of their team rapidly, flash is nice. The second you are in the middle of the enemy team and cast your ultimate, you win the teamfight.
Of course, just like in the lore, if Galio is overwhelmed, he probably won't win, so if you think that the enemy is overwhelming you, you can also use it to escape.
Keep in mind: This spell has a hack of a cooldown, try not to waste it.

Ignite
Type: Enemy target shot
Function: Doing damage over time and reduces healing gain
As a mid champion, you might like this spell a lot, because it can grant you early kills. The more kills you have early, the more items you get early, the more tanky damage you do early, the easier you win.
Keep in mind: Use this against either main targets (Attack Damage carrys and Ability Power carrys) or heavy self healing champions like Dr. Mundo, Master Yi and Fiddlesticks.


Optional:
Ghost
Type: Activation
Function: Grants you extra movementspeed
Replacement: Ignite or Flash
The function speaks for itself. With this spell you can also initiate easier and stuff.

Teleport
Type: Global allied non-champion target shot
Function: Teleports you towards your target within a few seconds
Replacement: Ignite
Gives you lane sustain. It is all that it does, but that is good enough for Galio at times.
Also: some people like to play Galio top, for them, this is even a better spell.
I would only take this spell if you are farming a lot in distant lanes and your team is warding a lot. So if there is any trouble with your team, and you are too far away, you can just use teleport as a huge gapcloser.
Keep in mind: This could be combined with Enchantment: Homeguard allowing ganking lanes in a very very efficient way.

The rest:
MEIYJHE DOES NOT APPROVE
NEITHER DOES GALIO

UPDATE: Dear clients, since some of you were not content by just getting the badass runes and masteries, I will explain a bit more about what is best for Galio.

There are so maaaaaany options, really, so many that work for Galio :O
You could go full tank runes, you could go full AP runes or even get GP10, I don't care, your game still will go fine.

Great Meiyjhe! Guide us to victory!
I will young student!
What to expect from runes?

MARKS
Primary: Offense
Options: Magic penetration
This one is obvious, I do not think that any other marks suit Galio more. You could get defense, but da defense be no friends with da marks. If you really want to go full tank, go ahead, spend IP on a half functioning rune! >:O

SEALS
Primary: Defense/utility
Options: Mana regen, armor, health, utility
The seals be swimming in the ocean, making it an easy prey for the One Man Army. Seals be friend with Galio because else they get eaten. But seals must not stack MR or AP because then the seals get weaker. Buy either mana regen, armor, health or utility for your seals. MR and AP comes later.

GLYPHS
Primary: Strengthing your spells, weakening the enemy spells.
Options: CDR, MR or AP
Whatever you take, you will get more damage with your spells, since MR grants more AP aswell. Just take the runes you already have, you don't have to buy any new ones.

QUINTESSENCES
Primary: A lot
Options: A lot
Add what you think is lacking. Whether it is defense or offense. Here I also won't ask you to buy new quintessences, just use the ones you already have, and look which ones suits your Galio style the most.

Well well young one, let's look to our trees, our... MASTERY TREES :O

What do we want here?
Get anything, ANYTHING! You could go full offense and do more damage, you could go full defense to tank more damage or go full utility for funsies.
You also could balance things out, but that's boring.
I ask you! YOU! BE INTERESTING AND DON'T CARE ABOUT 21-9-0 0-9-21 21 9 9 9 21 21 9 9!

YOU ARE A MAN! YEAH!!!
MEN GO PUT ALL THEIR MASTERIES IN ONE TREE!
AND IF SOMEONE THINKS YOUR AN IDIOT, THEN PLAY GALIO AND SCREAM: IM BATMAN!
Then they will respect you! >:D

Balancing is for ninja's and wussies, go full in one tree! Doesn't matter which one, they all work in their own way.

We are almost there young disciple.
After reading this you have enough knowledge for the sentinel.

For the start:
We want lane sustain, in order for early lane sustain we need either mana regen, defense or movement speed.

Thus we have the following options:
Doran's Ring
What is it?: The first tier
Cost: 475
Type: Passive
Function: Grants mana regen, Ability Power and health
Keep in mind: You cannot build this in a bigger item, thus useless late game, you need to sell it eventually, losing 30% of the money spend.

Crystalline Flask + Faerie Charm
What is it?: The first tier
Cost: 405
Type: Activation + Passive
Function: Grants mana regen and 3 potions upon each recall
New item, loved it instantly. You no longer need to buy potions, because Crystalline Flask can be used over and over and over again. For this reason, you do not have to be afraid to recall, since you get 3 free new potions anyway! The Faerie Charm helps you getting the Chalice of Harmony earlier, which we all want.
Keep in mind: You still have 70g left after buying these items, thus you could buy potions, but since you already have a few, you could also keep the money to spend it later.

Boots
What is it?: The first tier
Cost: 350
Type: Unique passive
Function: Grants movement speed
This is meta, for that reason I do not like it. As midlaner you do not really need boots anyway, but still get it if you really want to. With the preseason patch, this item got nerfed, making other options more appealing. Making this item less interesting.
Keep in mind: also with this item do not forget to get Health Potion and Mana Potion x2, without any mana regen, you are screwed!

Null-Magic Mantle
What is it?: The first tier
Cost: 400
Type: Passive
Function: Grants magic resistance
If you fear the enemy midlaner due to the damage output he can bring, get this item. Also this item can be built in to Chalice of Harmony rapidly, making it an useful option. It will also grant you a bit of Ability Power due to your passive, which makes it even better.
Keep in mind: also with this item do not forget to get Mana Potion x2, without any mana regen, you are screwed!

Now to the items AFTER the first:

Chalice of Harmony
What is it?: Second tier
Cost: 880
Type: Passive + Unique passive
Function: Grants magic resistance and mana regen
This is a NEED for Galio, granting you amazing mana regen and defense. The magic resitance also grants you damage! Needs no more explanation.
Keep in mind: You will build Athene's Unholy Grail much and much later, if you do not like that, you could get it earlier. Early game Chalice of Harmony will grant enough mana regen for you.

Mercury's Treads
What is it?: Second tier
Cost: 1200
Type: Passive + Unique passive
Function: Grants magic resistance, movementspeed and tenacity
Galio is the one man army, thus cannot be allowed to be snared. The tenacity will save you and thus your team many times. Plus the extra magic resistence is nice.

Enchantment: Alacrity
What is it?: Third tier
Cost: 475 + 1200
Type: Unique passive
Function: Grants even more movement speed
This is an upgrade to: Mercury's Treads. This will grant you even more movement speed, making initiates easier to do. Since we also already lost the movement speed bonus from Force of Nature, this should compromise it.
There are also other options, but this one is IMO most functioning. Enchantment: Homeguard is a lot of fun I must admit, and Enchantment: Captain is more supportlike. Take what you prefer.
Keep in mind: This is a boots upgrade, meaning that you upgrade your boots. Click on Mercury's Treads, go to the right top of the shop screen, and you will see all upgrades!!


Giant's Belt
What is it?: First tier
Cost: 1000
Type: Passive
Function: Grants massive health
I want you to be more tanky early, so, due to the lack of health, you really would like this item. You will also build this later into a Warmog's Armor.
Keep in mind: You could also get a Rod of Ages instead of a later Warmog's Armor granting you also a bit of damage. I prefer this way though because it is a more steady road early game and just grants way more health and survivability than Rod of Ages, thus I prefer Warmog's Armor

Chain Vest
What is it?: First tier
Cost: 720
Type: Passive
Function: Grants massive armor
Some people get lots and lots of magic resistance as Galio early, making them vulnerable for physical damage, so I want at least 1 armor item early, and yes I want a GOOD armor item. You could take Cloth Armor instead, but it doesn't really matter. You will build this in to a Thornmail anyway.

Warmog's Armor
What is it?: Legendary tier
Cost: 2650-1000 (if you bought a Giant's Belt)
Type: Unique passive
Function: Grants massive health and health regen
This is your first REAL item. This makes you a tank, GET IT!
Like mentioned before, could be replaced with Rod of Ages, though, I do not like it, it is a free country.

Thornmail
What is it?: Third tier
Cost: 2000-720(if you bought a Chain Vest)
Type: Passive + Unique Passive
Function: Grants massive armor and reflects 30% auto attack damage
This goes great with your ultimate due to the fact that that is a taunt, a taunt makes people attack you, thus thornmail is a great item. Besides, it is your only armor source in my build.
This the best option for armor to Galio.
Some might disagree getting this item early. Well, a lot of you disagree with getting this item early. I believe in balancing your defense early on. Getting a Thornmail will help with that, help ganking botlane early in the game easier. So, if you take this first, I expect you to gank bot lane every once in a while and maybe help top with the enemy AD bruiser :D
But indeed you could go for an early Athene's Unholy Grail ur sumthing.

Abyssal Mask vs Banshee's Veil
What is it?: Third tier
Cost: 2810 (A) 2500 (B)
Type: Passive + Unique Passive
Function (A): Grants Ability power, MR reduction and magic resistence
Function (B): Grants health, mana, MR and a nice spellshield
Since there is no longer a Force of Nature, we need an other item for some big *** magic resistance. There are basically 2 options for him, Abyssal Mask and Banshee's Veil. So it is clear, do you prefer more damage output or do you prefer more defense? Neither of these items will grant as much MR as Force of Nature did, but we will have to live with this fact.

Athene's Unholy Grail
What is it?: Legendary tier
Cost: 2950-880(if you bought a Chalice of Harmony)
Type: Passive + Unique Passive
Function: Grants magic resistance, Ability Power, Cooldown Reduction and mana regen
This item gives everything Galio needs, GET IT!
Keep in mind: You might want to get this item earlier if you think you are tanky enough. The stats are really nice.
Keep in mind: The new item Mikael's Blessing could also be seen viable, however, this is much more supportlike than Athene's Unholy Grail, for that reason, it is a lame item. But hey, it is a free country, make your own pick.

Rabadon's Deathcap
What is it?: Legendary tier
Cost: 3200
Type: Passive + Unique Passive
Function: Grants massive ability power
MUHAHAHAHAA YOU ARE A REAL ONE MAN ARMY!!!!
You tank everything AND you kill everything!!!!
You are now a REAL Galio!!!

We mastered a great deal here, but you are not ready yet! You will need some extra guidance!
So I will show you how to do certain situations optimal:

See:

I want to talk about this first because this is very very important. This applies for EVERY champion in the league of legends and should not be underestemated!

Especially as a one man army, you need to know as much as you can and use your senses to the full extent!

That means:

- Look at the mini map every once in a while.

- Know what opponents you are facing and what they can do (including summonner spells and items!)

- Be able to predict whether you can survive your actions or not.

- Be able to predict the amount of damage you can or cannot do.

By doing this, you will become a much better player and can allow you to reach the top of you master this skill!

Keep in mind: You also can hear! That means you can hear a nearby flash, a nearby emote and a nearby spell. This aswell, is very important!

Laning:

You, Galio the One man army, does not do any kind of burst damage early game, so for that reason we use sustained damage. That is the reason we took mana regen in the first place.

So poking and all is not so hard if you know how to aim. This will require expierence and cannot be thought by theory. It doesn't matter if you hit minions (Causing you to push) because Galio can escape ganks from jungler's easily, especially when having Mercury's Treads.

Escaping:

Oh my, jungler is coming? What do you do?
1. Resolute Smite the most dangerous opponent, slowing him, creating a bigger distance.
2. Righteous Gust a path towards your tower, granting extra movement thus using less time.
3. Bulwark yourself if they manage to hurt you anyway.
4. Flash if you are sure you will die if you won't use it.
Keep in mind: If you have your ultimate up, you can turn around the fight, making you the winner.
Bulwark yourself, use Idol of Durand and then try to finish them off with your other spells + Ignite. And yes, you CAN win 1v2! :D

Killing:

You are a smart guy so you saw (past form of see!!!) that you can kill the enemy/enemies (with your team), then do the following:
( Flash + ) Resolute Smite + Righteous Gust + Bulwark + Idol of Durand + Ignite
Basically these combinations mean: Initiate! Your ultimate allows a lot of damage especially early game. If you used your other main abilitys before casting your ultimate, they will refresh after your ultimate is finished! Allowing you to poke even more!
Of course only use flash if you are sure you cannot reach them, or you really want to suprise the enemy, however, you must always use ignite on the enemy, making him an easier kill.
Keep in mind: Of course, in 1v1 fights, be careful for tenacity. If they walk out of your ultimate, just cancel it by walking or something, allowing you to do damage still.
Keep in mind: Watch out for attacks from champions like Blitzcrank and Nautilus, that snare you when they auto attack. This will let them interupt your ultimate if you do not watch out!

Countering:

This is easy for you, because you counter pretty much everything mid due to your great magic resistence. The attack damage midlaners like Talon might be a problem, but just level up your Bulwark second and you should be fine.
Keep in mind: You are melee, so you cannot always farm that easy by auto attacks early game. Thus if you have trouble, just use your abilitys for farming, that is no big deal!
Though you might need some more mana regen than usual :D

The last part of being the one man army, is to fully understand him aswell.
I get questions about why I make certain choices and stuff, so here I will answer them:

1. Why do you not take Frozen Heart or Sunfire Aegis instead of Thornmail? (by Kersplakastani)
Well well sir, that is, because I want to do both damage as I want to be able to tank. The Frozen Heart will not give any bonus towards damage output except for CDR. This, even allows you to do less damage then you do without it, because the passive aura works against your ultimate, for it does more damage depending on the amount of hits you gain.

Why I do not take Sunfire Aegis is because it doesn't do as much damage as Thornmail does, grants less armor and gives more health, which we do not even really need.

2. What is your opinion on Twin Shadows? (by Doedesamba)
This item grants everything that Galio needs, even adding an extra gapcloser. However, the amount of MR and AP is not high at all, that means we would get this item for the slow and the movement speed. Since we need 5 enemies within ulti range and not just 2, the active wouldn't help too much anyway.
Also, taking this item means that you need to replace it with an another item. The only thing that this item could replace is Rabadon's Deathcap, since you are more with a tank role than a full AP one.
Taking this does not make you the One Man Army beast as Rabadon's Deathcap would.

3. What are your thoughts of Runic Bulwark, Shard of True Ice and Randuin's Omen? (by Athan)
Runic Bulwark and Randuin's Omen are typical tank items. For that reason only, you could consider it. However, since my build works like this: 1 big armor item, 1 big health item, 1 big mana regen item, 1 big MR item, 1 MS item and 1 big AP item, Runic Bulwark doesn't fit. You however could switch Randuin's Omen with Thornmail, but you will do less damage this way.
Randuin's Omen is possible in my build and Runice bulwark is very viable for Galio, but not viable in my build :P
Shard of True Ice is a waste of gold if you ask me.

Feel free to ask me anything anytime in the discussion, I will put them here and answer them.

Enough with the jibber jabber, go to the summary already!

Ladies and gentlemen,

Just a quick note, I will stop reading the discussion and updating this guide.
I noticed that the amount of work I put in doesn't come back out.

So, for you guys, I will keep this guide online, so you can still read it if you like it.
If you don't then I just suggest you don't, because I am not going to update this guide anymore.

I wanna thank those who supported my choices and enjoyed my guide.
Those who didn't, I want to tank you for your kind advices and still reading my guide anyway.

My work is now going to be focussed on my community guide, because I believe it fits my style more than champion guides. So if you ever feel like reading something of mine anyway, please, I still blog, help newbies and make community guides :D

Thank you all for finishing my read, I know it doesn't really matter if you read this on 4-1-'13, but I thought it is good to post it for the later days when mayor changes occur :D

May you find much happiness!
-Meiyjhe