When I first started Lol I was told to buy Darius and I got Volibear because he was a bear on frikin lighting. So I played them and a few other champions before finding Ezreal. I vaguely remember being told he was really hard to master but absurd to lane against. Now my friends at this time and myself had maybe 200 games between us so we hadn't come across many if any real players of skill. It was Ezreal's skill set that seemed so interesting to me. Either way I got Ezreal. And to be honest I sucked. I missed most skill shots, would arcane shift into enemies faces because at that level you just want the kill. You are not really coordinating with your support, thinking about last hitting or all the other things you should be doing, like measuring roughly how much poke you exchange with the other bot pair, or roughly considering how much armor they have and how much damage your abilities actually do.

An Unexpected Journey - Finding Ezreal or slipping into the role of ADC

Well I like to believe I have grown with Ezreal since those early days and I play a wide range of champions for all positions. I jungle well, and I solo lane well. I got my way up to level 30 by essentially winning half my games + losing half. But by playing champions who were not just ADCs or Ezreal I learnt about what they could do to me when I played against them - a factor that gives you an edge in any situation, with any hero in LOL. Either way, back then, if I got fed in a game then that made my day but this didn't happen a lot. Certainly not as Ezreal either. By this stage I wasn't a total waste of space with Ezreal, as I used him in about 70% of my games.

So I went to ranked in Season 2, ready to make my mark. To show them how much of a pro I am, for who could match me? A genius level IQ, a proficiency with games in general and having played 140 games I thought I was experienced. I could not have been more wrong. I lost my first two games, due to what I considered bad luck on my team, I cannot remember if they were with Ezreal or not. I then got trolled the next game which put me in a terrible mood. I then won the next two and entered ELO at 1100. Not a terrible score. But surely not the score a player of my caliber deserved right? Wrong. I realise now I deserved to be there, I played ~35 games in season two and had a win percentage of 38% - my average with Ezreal was 5/5/9 - not a score that says I was carrying games consistently if at all.

So season 3 came along and I was ready to make my mark once more. I entered, won my first game and got trolled for 6 games in a row. My new ELO was 850. WELCOME TO ELO HELL. The term didn't really mean anything to me before then but slowly I understood. Some players will say there is no ELO Hell. Well they are partly right. It is possible to win in low ELO queue and have a good team, I met players down there who are better than people at 1600 ELO - because the terrible teams force one to learn how to carry games for themselves quite often. It just so happens you are also more likely to be trolled as the trolls have low ELO because they lose games and they make you lose games. The hell part is you can have several good games and gain ELO only to lose it to an AFKer/leaver or troll or feeder/unskilled player. But then again. Is there any better place to be training your individual skill than in low ELO where you have the highest stress factors, and self responsibility for you to win a game rather than together as a team? Is there any training ground more suited to learning to harden your mind to the stresses of having the most stressful role? Is there any other place I could have learned to be an ADC of my caliber?

So the moral of this section is be nice, polite; learn to ignore the flamers, take the heat and remain level headed at the same time. You will become a beacon of balance around which your team can rally. Because after all. The game is never over till the 'Fat Nexus Sings'.A good tip is that if you lose three games in a row, stop playing. Not for the day but take a break, go for a walk or anything but be on LOL, it will do you good, and put you in the correct mind set of a cool, calm, calculating ADC.

If the ADC sucks, then you as the good support have to spoon feed them. They may fail to get the kills or do nothing with their kills. I.e. you are unlikely to carry the game.

The same goes for the ADC. If your support sucks then chances are if you are lucky, you suicide trade off kills with the other ADC, but at worst get out-zoned in lane (denied minion farm) + both get screwed.

I am a smart person. Most of my readers are too. But sometimes things are obvious only after being stated.

Forcing the Jungler to babysit bot basically means your top lane has a Jungler to help him + so does mid, with little to no fear of people ganking them, unless they are going to let you steamroller bot - and we all know where that should lead if your a good ADC.

This change, in what their Jungler has to do to keep bot from collapsing, has major implications. As maybe your other lane's summoners are idiots, or just worse/less skilled than those who they are laneing against. This does happen and I have made friends on lol with people I have fought against, as much as fought with.

The point is potentially neutralising the jungler is a major factor in carrying the game to victory, as your jungler may be able to help other lanes beat opponents that they otherwise couldn't 1v1.

First blood also motivates your team as it makes them think you are not an idiot and more likely to only focus on their own lane + problems. It will also undermine the enemy team's opinion of their ADC + Support - making them likely to flame and hamper their own odds of winning.

It can even mean players will not let teammates take kills because they assume that player cannot do anything with them - rather than their opponent is just better or even luckier.

On the other hand losing first blood and failing to trade kills can be a disaster for moral, but not a total defeat on bot lane.

I recommend strongly you duo queue with a support you know if you plan to ADC. Skype helps but a good support doesn't need commands.

Two of the best supports I have ever known and been lucky enough to play with were people I met by accident in solo ranked queue, and the only words between us were thinks like; "I love you, be my duo queue partner forever", and "you're epic".

So know your support.

I would also say as an ADC you need to learn how to support.
Why? So that you know what your support can do.

Duo bot as the ADC cannot be thought of in terms of just your 4 abilities and passive. You must consider the supports abilities to.

Why? Because you need to have faith in them backing you up and you're not getting that kill alone, especially that first kill if you're playing against a bot pair with a brain.

It also means you know roughly how much damage you can both do in x amount of time. As well as importantly how much your opposition can do to you with their duo bot combination.

So learn to play most/all of the supports, so in a fight you can act appropriately based on what they do and who they are.

Passing comment on dynamics you should be thinking about with supports (via an example):

Look at your team compositions. Some teams need to grind to the late game to dominate, or just the team fighting stage, as you may focus better as a team.

Additionally, even weak teams can finish the enemy base in a minute if they manage to ACE the enemy and the enemy is waiting to respawn.

So do not get disheartened if you give up a kill or even two at bot. Your jungler can be called in to baby sit you and save your game, just as much as theirs, as well you being to play your way back into a strong position vs. their Bot.

Do not just give up. After losing a few games in S3 with Ezreal I looked for advice online, that and due to playing with certain people and all the things mentioned in this guide, I can carry games consistently and with minimal feeding.

Smart casting is a must on Ezreal for Q, W, E, + R. Because if you get that attack off first you will kill them first.

For those who do not know what smart casting is:


With Ezreal I start the game saying half my mama is expendable.

This mana is to be used on last hitting or enemy champions, leaving me enough mana to use abilities for a duel if and when it happens in bot lane.

If you hit q on the enemy ADC, then your ability goes off cooldown, and if the enemy fails to heal all the damage and then both bots try to kill each other's ADCs, assuming your runes are appropriate, you will likely walk with first blood, especially as Ezreal, as e can be used to disengage (as it is probably cooled down after the fight).

I usually try to hit three Qs on my enemy ADC to burn a pot or two, then engage in with my support leading the charge, taking care to put myself behind my support so any abilities like my own q that do not pass though multiple foes, doesn't hit me and hits my support. 7

Because chances are if I kill their ADC and then my support dies, their support is going to leg it or die.

Another point to consider is that if you kill the enemy ADC + can make the support get the kill on you or your support, because you cannot escape, this is a more than acceptable trade off.

A more advanced tactic is to also consider your minions' positions as they will auto target the enemy champions if they aggro you and they are close to the enemy. This can be very powerful in early game and still give you a worthwhile advantage mid game.

This again comes back to smart casting as a must. Personally I have Q, W, E on smart cast, R as it is normally set up, but setting my ultimate's smart cast to space bar to fire it if I need to - especially if the enemy is in my face (And note: I use space bar for everything, as it also means it is hard to miss-click your R).

Other big reasons smart casting is the way to go:

By smart casting your e, you basically have a skill functioning like flash. Instant flash, which is what makes flash the favourite summoner spell of most of the lol community.

Now that I have covered the likely bottom lane first engagement it is also important to consider an alternative situation that does happen.

If you are purple team + they are blue they may go for bottom Golems for gold + exp.

This serves them well if you allow them to heal up.

Chances are their support took the agro vs. Golems, and even worse, chances they did it with a support who can heal the damage back with abilities.

In this situation I would recommend harassing their support, keeping them low and then at level 2 aiming him down. Again to max your chances of first blood and to counter their potential level advantage.

In this situation I would say it is situational who your support uses exhaust on as you may want to counter the damage their ADC is trying to do to you as the ADC, or stop them running, which is why I love Leona as a support with stun and gap closer. Stuns are funs!

-Stay closer to minions
-Consider type of minion - casters take less damage to kill but deal more + melee minions take less damage + deal less
-Skill shot minions being overwhelmed by minion attacks rather than timing it, as you are more likely to get the last hit
-Move side to side to avoid shots - not away, as you want to zone them around the minions and improve last hitting
-Watch number of incoming attacks whilst watching minion health to time attacks
-Learn how long it takes from different ranges for attacks to connect
-Consider what is the delay between attacks (The minions + your own)
-Get used to your attack animation in custom games + real ones.
-Pressing A then miss click on bush -/-> move? Insta-attacks enemies in the bush - this is just such a ridiculous tip.
-S to stop attack?
-Push lane before recalling to deny farm as their tower eats your minions
-Push lane after a kill - when appropriate - again to deny minions before you recall to use your gold to widen the gap power
-Bully opposition in lanes away from minions occasionally - best time to do this is when there are not lots of minions you need to focus on LHing
-When not close to a last hit harass the enemy, that is the best time to do it
--Watching the minions your enemy will go for will also help you predict where they will be. Also when they are locked into their attack animation they cannot respond.
-Do not forget to farm the jungles occasionally if they are free to farm when not in lane
-When farming under a tower. Provided you buy a long sword at the start, you will be able to kill with you aa, melee minions who take two tower hits, or a caster who takes one hit.
-Use skill shots to last hit minions after you LH a minion with your AA. Makes for more efficient farming.

Important! All other guides say "here is your ability combo sequence to attack/engage", this I believe is a huge flaw and is nurfing your damage without most people realising.

With Ezreal be sure to time your abilities between your auto attacks as otherwise you are missing out on free damage, or killing minions when you can basic attack one + ability shot another (getting to Last hits).

Using an ability resets your attack animation. This holds true for aiming champions down.

Yes spamming seems like a good idea, but lets us say the enemy ADC has a Dorans blade on a hero and you do not (Saying this now, never buy one. It is money down the drain. Get a long sword if you want Damage - will talk more about this later).

They then spam their combos, over their auto attacks (interrupting them essentially), whilst you do not, so timing your abilities between your auto attacks, you will be appalled to find you will do more damage!!! despite their apparent item advantage!!!

This is very hard to master. But it holds true for all ADCs - but most strongly for Ezreal who has all skill shots.

Mastering this skill is the sort of thing that allows you to turn bot around if they are a kill up at the start - or otherwise in a race to kill the other guy before they kill you.

It has greatest impact early game and mid game when your attack speed is still low.

This simple tactic allows me to carry games, early on and therefore snowball, at ELO where I am otherwise usually being out farmed by my opponent (although not by that much) who potentially goes for early extra damage (e.g. Dorans), a level up on me or has some other minor item advantage.

Remembering to use w on allies is hard.

You're dealing with a lot of stuff in team fights, but this ability can turn fights. +20% attack speed is simply the most ridiculous ability to have on an ADC because it basically lets you buff your team's damage for 6 seconds.

Of course using your w to hit multiple enemies is useful but you are not building AP, you do not want to get the most kills in a team fight that your team loses, you want your team to win the damn engagement.

It is important to remember late game, that your w is actually nurfing your (solo) damage output as it takes longer to cast than you can put out two auto attacks.

So use it when your team is no longer buffed by it's effects in a team fight. Not when you are intent on dealing as much damage as possible to a single foe you want to kill as fast as possible.(I know right. Like we need to be paying attention to the clock in our heads for when it cools down, on top of all the other **** we have to remember and keep in mind as ADC. Are you certain you really should be reading this? Go away. Have a nice life. Play easy roles. What? Still here? Fine...Then carry on. BUT I WARNED YOU!).

Sniping:

Other good times to fire your ultimate:

This is an Ezreal ultimate. It is a flying bannana of doom, that has global map range and a 12% reduction on each consecuative enemy hit. It has been known to kill many a hero & steal many a Nasor. The question is do you feel lucky?

Knowing when the shot is worth it:

"An outside context problem. When suddenly this bristling lump of iron appears sailless in the bay and these guys carrying long funny-looking sticks come ashore and announce you've just been discovered, you're all subjects of the Emperor now, he's keen on presents called taxes and these bright-eyed holy men would like a word with your priests."

Changing your ultimate's fireing direction after you start channeling:

I want to preface this section by saying this is a rough section. No guide can full proof tell/teach you the best way to position yourself in a team fight as basically every fight is different. I also want to say this section has less focus than the others here. This section is more of some of my musings + discussion about positioning which may contain something that might help you or hopefully help you view the team fights in a different way that changes the dynamics of how you act as well as how the fight ends.

So with my *** comfortably covered I shall get on with my advice on position.

Firstly. Paranoia as the ADC really is a comfortable state of mind. The moment you drop your guard you bring disgrace to yourself, me, and all other ADCs.

One of my friends who has trouble as ADC says his main problem is reminding himself to always stay two steps behind/back from the enemy. This isn't exactly the case.

It is more important to convince yourself + understand you are the ranged ADC.

Firstly you need to know how strong whoever you, a pair of you or your whole team are compared to who they are fighting and roughly the escape options open to those you are about to attack.

This can be roughly guided by glancing at how fed heroes are on the enemy team, what items they have + their summoner spells, compared to your own.

The idea is to identify the enemy team's weak links; e.g. Malphite is scary because of his sustain, but doesn't do a lot of damage. Therefore aiming him down is a terrible idea. Even if he isn't that fed or fed at all, the tank is not the person you want dead first.

The person you want dead is the one who is dealing the most damage. Chances are this will be the enemy's jungler, ADC or APC.

Now it is important to remember most junglers are quite tanky and are likely to each scale nice health or armor +/or Magic resist. So even if they are fed up the *** and lethal, due to their likely move sets they are unlucky to be able to kill everyone on your team in 5 seconds. At max they are likely able to aim down one of you rapidly + a second fairly reliably.

Now the ADC + APC are a different story.

The ADC in theory just shreds everyone + the APC uses spells to nuke everyone.

An APC is more likely to do AoE damage to the team compared to the ADC. This makes their damage spread out.

This is a good + bad thing as it means everyone they hit is easier to kill but it also means the team fight stays a 5v5 for longer or on an equal footing.

Even with APCs that nuke people like Veigar or LeBlanc, once they have killed someone they will back off if possible to await cool downs to finish - before coming back for more. This means that they are neutralised from dealing super damage for a brief period. This time will usually be sufficient for the remaining people on your team to kill someone.

The person you want to kill is probably their ADC, because they are usually dealing continuous auto attack damage.

Having items like quick sliver sash or cleanse as a summoner spell are useful if you are the ADC to stop you being trapped + focused. Particularly on a hero like Ezreal where you can reposition with your e (although I don't personally think cleanse is a good idea on Ezreal unless every hero in the enemy team has a stun...and even then).

With the ADC dead and you hopefully alive it is time to hit the next threat. This, in the ideal world, is probably their APC. However you will need to judge who to go after next - it is best to then go after who you judge can kill the most people on your remaining team or turn the fight in the enemies' team - it is also important to have your team know the plan of who to kill in what order.

But you must consider how long it takes it kill someone.

Someone who can kill two allies but takes 6 seconds to aim down means someone/multiple people on their team has 6 seconds to kill you or your allies.

The right person to kill is someone who can be killed fast enough; that the time their death buys from you not attacking other people, is not enough time for those people to decrease your team number by a similar size or neutralise their key targets.

This is a very hard thing to master and something that is more important at higher ranked ELOs - as it requires the whole team to have good awareness.

Regarding the order of who to focus - this is something that should be clear - I.e. order of enemies to focus down - to the entire team prior to an engagement.


With a hero like Ezreal, after the first target is dead, it is tempting to reposition to kill their APC. This is a good idea provided you are fairly certain your team can protect you whilst you do so, but trading off yourself for the APC or target number two can be a disaster as you may be the only one fed on your team - so the only person doing damage, you may be the only person with a brain and a hundred other reasons.

The point is that if people are dying on both sides during the team fights, and it isn't a one sided slaughter, you ideally want the fight to devolve into you (the ADC), a tank and a jungler/support, whilst the opposition has lost all its damage dealers. Ok what is left are Tankier heroes, who are hard to take to zero health but they are unlikely to be able to do enough damage to kill what you have left - or match the damage you will output.

At this point it is ok for you to back off a bit to secure your safety, usually standing behind your Tankier allies. Even if your allies will take damage as a result without you trading damage to their attackers it is you who is meant to carry this game, you who can kill them by doing the most damage.

Also it is impotent to identify if you are on acceptable health or mana to stay in the engagement.

Sure winning the fight is nice but this shouldn't be done at the expense of potentially feeding enemy heroes unless this is the final showdown + you're three cm from their de-towered nexus and average respawn time is over 40 seconds - so no one can stop you winning.

It is also important to then, if you feel you are at serious risk of being a risk of jeopardising game outcome by sticking about to evaluate your allies situations.

Are their deaths with you running assured? If so, is you living going to really help? Can they get away if you act in a certain way to help them get away - if that is the best outcome from this fight?

I will not give you any advice here because there is none.

What needs to be done + what you do will be up to you there and then and again will be different basically every game. I talk about all this to make you aware of some of the things you should be considering.

The best advice I can give you is that when a team fight starts you shouldn't necessarily be joining the other four members immediately. It is better to let the fight start - view the situation and then position yourself where you can contribute whilst remaining safe.

This serves several purposes.

The most obvious one is keeping your squishy ADC self safe. It will make it hard to aim you down as most ultimate's get blown in fights early on, have limited range and most stuns will be used by a team to engage the opposition. Another obvious reason is being able to get the lay of the land to figure out how you will want to move in the fight - I.e. go from one prime target to another and go after people who may be killable in a second or so by you alone - if their deaths will help your team win the fight or if their team cannot stop you killing them.

The last point I want to explore is what your role can also be used for.

As the ADC and the likely person the other team wants to focus, your movements can be used more than any other team member to bait the enemy.

You can control the set up of the team fight as your team + you can reduce, and deduce the likely positions people will take when the fight starts if they are trying to reach you, or when they engage.

This can be used to get someone to preemptively engage or over extend, use an ability etc and basically position themselves poorly because they think you are about to be locked down.

As Ezreal with a large flash distance, you can bypass their attempts to lock you down, with either of your flashes (+ with good reflexes and eventually reaching the level where you like me can catch the micro animation actions of most enemy heroes that give me a split second bit of knowledge that they are about to use ability, x, y or Z). This requires lighting reflexes, very low ping and comes with experience of recognising the animations enemy champions make before they finish casting a skill shot or use/recognise the animations to know which ability is about to be fired. This comes from experience of playing other champions.

Note: Color coming to this section soon.

The decision to start with a long sword with two health pots is that the pots heal you and the sword helps with poke + last hitting. The plus 10 damage really helps with farming under the towers as you can kill a caster minion that is on full HP after it takes on tower hit, rather then basic attack it once, let the tower hit it and then last hit it - as is the case if you start with boots + three health pots. Taking no boots on Ezreal at the start is very viable due to his e providing him a repositional flash.

The decision to go for a BF sword instead of the classic boots + vampiric sceptre on the first recall is due in part to you having enough for a BF sword and probably not one of the other two on top of that (the first recall is likely after one of the ADCs gets a kill) with the person who killed the other likely staying in lane long enough to push the minion wave to the tower so the minions get eaten by the tower.

The main reason I go for a BF is not only does it make LHing a breeze early on, it means you are doing a serious amount of damage to the enemy. Your q's range mean you can poke very aggressively and zone the enemy from lane nicely. The BF sword also means that you in a protracted fight with the other bot pair will do more damage than what they heal with the classic vampiric scepter. The counter point many people will argue is that they will likely have boots and so can run in + poke as well as disengage more effectively that you, meaning they trade more often. But your q's range is enough to hold them at arm's reach. And as I said. You are trading harder than them now. So if they try this + you are half good, you should be able to q + auto attack them when they run in, again allowing you to trade harder. The only exception is Caitlyn who just ***** on all other ADCs pre level 6 as she can harass safer than any other ADC - with no mana cost. In the case of fighting Cait, I argue you start with boots + vampiric over BF, if things are going well as you want to be conscious of her strong ability to force many bot champions out of lane quickly due to her harras.

I choose BF because I play very aggressively at bot to force the gap in terms of our gold as wide as I can either by securing me another kill or harassing so hard they are too scared to farm properly because I have zoned the area around the minions.

Building onto a Blood Thirster is done on the basis of giving you strong sustain - to keep you in lane + therefore farming for longer, if + after you take damage.
The fact it stacks +1 damage + 0.2 life steal for every minion you killed is free damage in the bag.

Now you buy boots. Although depending on how far into the game you are, you may wish to prioritise buying basic boot (Because you buy a boot. Not boots) over completing your BF (for 850 gold) first.

The decision to go with a Phantom danger is to stack Crit Chance, attack speed and in my opinion to get one of the best passives an ADC can have (walking through minions) - keeping you safe and providing you mobility in many situations that will serve to keep you alive. Many argue a valid second buy is Stattik Shiv, as it does AoE damage and on hit effects like with your Q and this damage can Crit, meaning you do more total damage - plus it helps with farm. This is true however the Iceborn provides you with a better AoE effects (an AoE slow and damage to surrounding enemies) and the phantom dancer gives enough benefits that the time Shiv helps you shave off farming is around 3 seconds tops. Phantom dancer however is more consistent and better for killing single targets than spark (duo to consistent and total dmamage output on a single target rather than total damage output), which I argue is more important in terms of fulfilling the role of ADC and ties in with my style. Feel free to swap out the Phantom Dancer for a Shiv if you prefer it - it is all about what you are comfortable with. Also the farming difference between the two is almost negligible once you rock your Iceborn gauntlets.

Note: now is when you can start using your R to farm lanes for more than 1-2 minion kills which would be a waste.

Iceborn gauntlets seems to me the item Ezreal could only have dreamed of. Providing large amount of armor, enough mana to mean you have no worries for the rest of your days, it's our problem free philosop-...apologise. Childhood memories of the Lion King compelled me. It also gives you a slow that applies instantly with your Q + following your other abilities being used which applies on your next auto attack.
Simply put it allows you to catch enemies, stop people following you, ruin people's engage abilities, stop allies coming to each other's aid, control enemy movements in a team fight, farm due to the AoE damage, stop enemies following/catching your allies and more.

Iceborn gauntlets being bought on my game is a huge action for me - it basically marks when I stop dying for any reason as I have high levels of control over my environment - and a great way to keep myself alive. No matter how far behind I am in a game, once I have my first three damage items I feel confident I can turn a game around. It also marks the time my farming starts going through the rough in a fashion that makes even the most fed Talon's rake look bashful.

Now this is a personal thing. I buy level two boots of the berserker after my Iceborn gauntlet to maintain a gold advantage that is being pored into my damage output. However buying it before you start building sheen to go to Iceborn is totally up to you. Hell I see no issue buying it after I buy Sheen and before I complete Iceborn Gauntlets. I am just very confident in my positioning and flash response times to often not need level two boots till a bit later. Which brings me into a point. Boots level 2 are a waste before you have two major damage output items like Blood Thirster + Phantom Dancer as your damage output before then is still primary coming from your abilities. The other reason I buy Phantom dancer is to allow me to delay buying level 2 boots as it give a movement boost passive. This again makes for more efficient gold spending to damage output you can use to make kills. The idea is to always establish a damage advantage you can use to widen the gold gap as wide as you need to carry the game fully.

The other items thereafter are situational. The blade of the ruined king, Last whisper or Black Cleaver is what I recommend buying next to deal with enemies rocking armor. They way I see it Last Whisper is better for you killing enemies, whilst Black Cleaver is the more team friendly item to buy; as it lowers the armor for everyone for the duration of its effect.
When deciding between the two I would say use your score to guide you. If you are underfed compared to their ADC - go with the selfish route of Last Whisper, where as if you are fed, like Goku after eating lunch, you should help the team score kills and taking Black Cleaver is better for this. Going for blade of the ruined king provides great sustain and a way to deal with enemies with huge armor or health (I am looking at you Cho'gath).

The rest of the items you buy are up to your own ideas of what is needed that game. I have given some variations on final builds above.

x9 AD Marks & x6 ArmPen 3 AD are very viable on Ezreal.

ArmPen x3 AD allow vicious damage potential without penetration items, but will influence your early (20 minute game) farm a lot.

On the otherhand, the classic 9 AD marks allows for great last-hitting and the usual lane control.


ArmPen x6 is a joke vs. minions due to their extremely low armor, which laughably make ArPen unnecessary.

Having the classic 9 Armor seals are stock standard on all ADCs for a REASON, because they nullify/dampen damage from enemy ADCs, enemy supports (autoattacks/otherwise), minions, towers, and junglers. Unsurprising really that armor protects.

It is considered viable to have x9 MagRes glyphs and x5 MagRes x4 Mana Gen.
The idea here is that x9 MagRes mitigates damage from enemy carries and mostly damage from supports.

If you're bot laning against a weaker, magic damage dealing, support such as Janna, Nunu, Taric, Soraka, you could take Mana Gen/ lvl to aid mana problems later on in the game - however your Frozen Gauntlet should be keeping you nice and mana plentiful.

Many argue that 3 AD quints are necessary to control your lane and last hit under tower however I think it is just as viable to have these as armor penitration if you reduce your number of penetration runes and increase the number of AD runes. Alternatively Embracing in his Internet Explorer Ezreal guide makes that point that "you can also take one or two Lifesteal quints to help sustain in lane, but if you do so it's best to take 9 AD marks for the farming."