I was actually thinking of doing this post a little later, but since the Lich Bane patch is still topical, I felt this was good timing.
So first of all, why even AP Ezreal?
As far as I could gather, AP Ezreal was a semi-popular thing at a time prior to me joining League a little over a year ago, and has since kinda lived in the suburbia of the meta: acknowledged as being a thing that happens, but no one really bothers with or pays attention to. If you feel that this isn't true, that Magic-man Ez was or is more/less popular than I make it out, that's fine. It's not really relevant to this post either way. I'm talking about AP-Easy right this second, on this current patch, in season 4.
The first thing you should go do is take a look at the Ezreal entry and just familiarize yourself with all the scaling on his abilities. I say this because, as I have learned, most people forget that Arcane Shift actually does damage, or that is W is more than just a team attack speed buff. Because if you're playing AD Ezreal, that's all you usually need to know.
Have you gone and re-learned Ezreal's abilities? Good. Let us continue.
250 base damage plus 80% AP on his W. 275 base damage plus 75% AP on his E. It's hard to argue with numbers like that. The only current competitors are Gragas and Morgana, with Morgana beating Gragas by a margin. Then why, pray tell, would someone pick Ezreal over someone more meta like Morgana or Gragas? Well, the fact that he has a range advantage over the fat man helps. Plus, he can more reliably land his damage across all 3 of his abilities, one which automatically targets the nearest champ, rather focusing on not whiffing his barrel/body slam combo. He is obviously more mobile than the Fallen Angel, and his primary damage spell (his W, if you were still confused about that) isn't blocked by minions. I can't stress how big a deal this actually is. Everyone is so used to AD Ezreal, they don't realize in-game that he has two skill shots and minions only help with one of them. They know in the front of their mind “Yeah, it's AP Ez, so I need to mind his W”, but they see the Golden Boy on their monitors and subconsciously go “Watch out for his Q, stay behind minions” and forgot all that magic damage you have. At least until you kill them a few teams with your Ult>E>W rotation.
Ah yes, his Ult. 90% AP. 650 base damage to the first thing hit at third rank. And it's magic damage, so all that magic penetration that you normally don't build on AD Ezreal further boosts the damage.
But obviously there is a drawback. The first is that while your opponents have to relearn how to play against you, you must also travel along the adjustment curve for playing AP Ez. That usually means remembering that Your Q stops being useful after level 4, at least until you get a Lich Bane (but we'll get to that later). The second drawback is oh god where did all my mana go I swear it was here just a second ago. Blue buff fixes this, but if you don't get it, you can only really spend a maximum of 3-5 minutes out in the rift before you have to recall. You can keep some pots in your pocket, but they clunk up your item slots and really…..those should be wards. Athene's will go a long way towards remedying this as well, and has a lot of other features that Ez will like. But I will get more explicit and in depth with itemization later. For now, we talk about in-game play and strategy.
The third and final drawback to AP Ez is his early game. And By early game I mean the first 4 levels. He is very squishy, and he lacks the true zone control that lets others like Orianna and Ziggs to bully people in the first few minutes of play. Furthermore, you need a few ranks in your W before your damage starts to ramp up. And you will be ranking your W first. Your E has too high a cooldown and mana cost to try and invest those precious early levels in. Some people maintain that even with AP Ez you should go for early ranks in Q. Why. Why would you waste your potential damage spike at level 5? Your Q's base damage is abysmal, and only gets 50% of your AP. If you are going true AP Ez, you won't have any AD bonus, so the early strength that normal comes with the 100% AD ratio is irrelevant. Your Q is an important part of your kit, with delivering Lichbane procs and all that. But you don't have a Lich Bane at level 5. Dumping early into your Q is just going to shoot you in the foot, and you won't be able to match the damage of your lane opponent.
As I hinted at, while the early levels are pretty rough for AP Ez, you do hit 3 big power spikes in the early game, all in quick succession. The first is getting your hands on a Sheen. Much like a Fizz, this should be your first priority, and should be achieved by level 5, no later than level 7. I easily forgo boots on my first back if it will allow me to by the Blue Blade. Having a Sheen means you can poke with W and then follow up with an easy auto for great harass. It is very much like Zigg's Q+passive damage, except you only have to wait 7 or 8 seconds to do it again. Your second power spike is getting your Ult at Level 6. It is a little tricky to land due to the long wind up duration, but If you can lead with your Ult, rather than sniping them in the back with it when they get away, you can all in someone at level 6 for an almost free kill.
Your third spike is when the Sheen is finally transformed into a Lichbane. Even though the damage on it took a heavy hit, it simply works too well in Ez's kit to pass up. You can deliver it through your Q every 3 seconds; you can W+auto, E+auto: it just really puts the mystic in Mystic Shot. If you don't get it, you will essentially never use your Q except to farm very slowly. The CD reset is great, but without some punch to back it up, you might as well go for a DFG. But again, I will es-plain more of that later with items.
After you have hit all three of these power spikes, you should be dominating your lane opponent. While he is weak early, it's hard to catch him out due to his E. He can safely harass with W and last-hit with Q. And dat scaling doe. It's very hard to lose an advantage as AP Ezreal once you get a hold of one.
Ez is one of my favorite champions because of his versatility. His kit is very flexible and really rewards players that are able to react quickly and adapt their play style on the fly. As AP Ez, you can go aggressive, Arcane Shifting into the enemy and burst them down; or you can play defensive, kite, and poke them down. You can use his Ult as an easy follow up to your Amumu's great engage; you can use it to help keep far away lanes pushed; or you can use it preemptively to deter they enemy team from committing to a fight. But we are once again getting ahead of ourselves.
Mid game you can catch people out with your E>W>Q+Lich Bane Burst, or you can siege up around objectives and poke people down. As I said before, his E grants him great mobility, and you can quickly get your longer cooldowns much shorter by using the reset on your Q. With a good 20-30% CDR, your Ult should be up every 30-40 seconds.
AP Ez transitions scarily well into late game. His really high ratios allows him to make a lot of use out of a full 500 AP-carry build. And all those skills will be on very short cooldowns. He has all the tools that AD Ez uses to make those late-game team fights work: his passive that fully charges off a good 5-man Ult, a W that gives the rest of his team a strong Attack Speed boost, a blink that could potentially be a double-blink for extra safety while roaming the jungle. The only thing you have to watch out for is running out of mana when you should be sieging inhibitors. Keep both blues warded, and don't be afraid to fight for them.
And now for Items. I hinted at a few earlier, some seem pretty self-explanatory. But just as there is much versatility in his play style, Ez has much versatility in his build. Especially as AP-Easy. As it should go without saying, item builds should reflect the in-game situation. There is no static item build that you can use for every situation; you should be able to deviate from your “core” in order to better itemize against your opponents. The following is merely the outline for the “core” as well as some recommendations for how to itemize for certain strategies. I won't talk about defensive items much because those are also situational and don't really interact with AP Ezreal specifically.
Lichbane I feel is pretty core, despite the recent nerfs. Good AP, some mana to help, some movement speed to emphasize his mobility. I'm sure you could manage without it, but it would be a radically different approach than what I am used to.
If Lichbane-less is something you want to experiment with, you will probably want to look at DFG. No Lich Bane means you probably won't be Q-ing people, which means you won't get CD resets, which means you want to further enhance the massive burst of magic damage rather than constantly spew spells for sustained damage. I have not done it too much personally, but Ez can function very much like an assassin; Shifting in, tagging with a DFG, then W>Ult to drop a carry. A Lichbane will still help this approach, but if challenging the sheen-dependent Ezreal is what you are going for, you can use the slot normally occupied by the Lichbane for another massive AP item.
The mana problem can be solved within Ezreal's build. Athene's is an all-around fantastic item that works for any AP mana-user. Ezreal especially loves the CDR, and the magic resistance helps in the defense department. Note that this is less useful for keeping your mana topped up through a fight, as you can still easily burn mana far faster than you can replenish it. But it allows you to do a short skirmish, and then regain your mana while you move to somewhere else on the map, and have your mana near-full by the time you get to your next destination.
I myself have been experimenting with using a Tear of the Goddess to resolve the mana issue. Less regen than an Athene's, but the deep mana pool means that drawn out fights or sieges are not a problem. I simply need to be mindful not to overextend and try not to run out of mana before I can get the chance to back to base. An Archangel's Staff also synergizes with the mana you get from Lich Bane. I don't think I would go for the full “Rhyze Trinity Force” of Archangel+Lichbane+Rod of Ages, but each bit helps.
Nashor's tooth is something I have been on-and off with. It syncs well with the large portion of Ezreal's kit. He already gets passive attack speed, so getting a Nashor's will keep Ezreal's damage output relevant for the brief 3 seconds he has between a spell rotation. Plus, his Q delivers the Nashor's damage as well. That gives your Q a total of 232 base damage at level 18 with 115% AP scaling; 115+65%AP will be magic damage benefiting from whatever penetration you have.
I didn't mention this before, but you need to keep in mind that your regular Q damage is physical, even with the AP scaling. You won't be itemizing for armor penetration, and the new hybrid pen mastery can only go so far, so getting a Lichbane is the only way to keep your Q damage relevant. It will be passable right up to the point that the enemy team starts to itemize for people who aren't you, namely your team's actual ADC. Even the enemy ADC might eventually grab a Guardian Angel, which will moot any physical damage you output.
So I will talk a bit about counter-picks to AP Ezreal as well as team-comps he fits well. Again, you should keep in mind that skill is a big factor, and you can't just insta-win lane by avoiding the wrong matchups. As I said before, AP Ezreal is a generally safe pick with great late-game scaling and flexibility. But there are things you need to be aware of when you are in champion select
Generally, people who are able to either match or negate Ezreal's mobility match up well against an AP Ez. Rhyze, while definitely not popular, doesn't give two cents about mobility. He has a targeted snare and all his other skills are targeted as well. He also has a generally beefy build that spikes in power at around the same times that Ezreal does, making it difficult for Ez to scale against Rhyze into mid game. Yasuo is another scary match up for Ezreal. Yasuo is mana-less and will generally sustain better. His shield is less of a problem since Ez can prematurely trigger it with an auto attack, but his Wind Wall blocks all of Ez's skills. You can arcane shift to the other side, but then you are either in melee with a melee ADC (bad) or Yas can just dash to the other side of his wall (not as bad but very frustrating).
Zed is another potentially scary matchup. You can't kite his Ult, so it means that a Zhonya's might almost take precedence over a Lichbane. And Leblanc, hyperbolic-ly, is another big problem. There's no chance to Arcane Shift Away if you spend 1.5 seconds silenced and another 1.5 seconds snared.
Magic Man Ez does have a good foothold over other currently popular mid-laners. He just straight up out-damages Ziggs, and can use his E to chase after a flying yordle or dodge his AoE. Ez lanes well against Gragas in a similar fashion, being able to consistently dodge a Q>Ult>E combo by blinking. Orianna less so, but he can match up against her prolonged damage in a drawn out fight with Lichbane procs and CD resets.
As far as team comps go, the versatility Ezreal has allows him to find a role in almost any team strategy. Poke comps? Not a problem, got Q's for days. All-in Engage? Press R for instant follow up, then Shift in for massive damage. Pick/Assassination-Comp? Get some wards and get ready to Shift over every wall in the jungle. Split Pushing? Ult one lane while you push another. Caught out? Just keep Shifting, just keep Shifting…
I would say that Ezreal does suffer from the “Jack of all Trades” problem, where there are usually better specific picks for the strategy you are going for. For example: Ziggs pushes lanes heads-and-shoulders above Ezreal, sieges better, and can do the double lane push with his Ult as well. The advantage to an AP Ez mid pick is when you are picking first in draft, you're not sure what your opponent is going to pick, and you need someone who can let you adapt. Or maybe you want to throw the enemy team a curveball so they try to organize their bot lane thinking that you will be ADC.
Well there you have my thoughts on AP Ezreal. Go try it, catch some people off guard. Maybe, like me, it will become less of a crazy curveball pick and turn into something you actively pick up. Happy Essence Flux-ing!