Irelia Build Guide by DiViNeSouL
Not Updated For Current Season
This guide has not yet been updated for the current season. Please keep this in mind while reading. You can see the most recently updated guides on the browse guides page.
Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Hello! I'm DiViNe SouL, an EU player, new to this website. This is my first guide, and I chose to make it about what I do best, offtanking Irelia. Before reading this guide, I you should be aware of the whole 'offtanking' concept. I strongly advice you to read this guide before reading mine; http://www.mobafire.com/league-of-legends/build/offtanks-the-new-metagame-79701.
Note: There seems to have been a lot of misconceptions regarding how Irelia should be played. Most people tend to play her as a DPS, and I'll explain why that's way off later in this guide.
This guide is adapted for the current metagame, for what works against the most common lineups today, and what works well on Irelia after the nerfs.
Offtanks In General / Why Irelia?
In Duffs guide, Irelia is considered one of the best offtanks in the game. I couldn't agree more to this, and the explanation why is pretty simple. As an offtank, your main objective in teamfights will be to jump right through the enemy team composition, and taking out squishy targets as soon as possible, while actually tanking for your team. For this, there are a few things that are required. I'll list these things, and explain how Irelia makes up for them.
- High Base Damage - So that you won't have to actually itemize DPS too much. These kind of champions usually scale pretty badly with offensive items - an Infinity Edge for Ashe will affect her damage more than and Infinity Edge would for Irelia. The only item you'll always get would be Trinity Force, and a champion scaling really well with that is an advantage.
- Mobility - During mid and lategame, your champion really needs to be able to pick off targets, and move to the next one, as fast as possible. It's really important that your target won't be able to run away, since chasing the target will get you away from the teamfight.
[Offtanks get high mobility from Trinity Force Passive and Movespeed buff, Randuin's Omen active, and Force of Nature Movespeed buff, but having a generally mobile champion does help.]
- Lane Sustain - In order to farm up a champion properly, you need to be able to stay at a lane for as long as possible. Your starting selection of items will help you do this, but it does help to have a champion that's good at lasthitting pretty aggressively at a lane, without getting shut down.
[Offtanks use Philosopher's Stone, Rejuvenation Bead, and sometimes runes, in order to be more sustainable in the lane. Still, having a champion that have abilities to improve this help, since only earlygame items usually won't help you lane so much that any champion would be a solid laner]
- Initiating Abilities - You'll find it pretty hard to break the enemy team composition when playing a champion that can't initiate well. The squishies that you're trying to take down are usually the ones placed in the back, every champion can't just run through the enemies and start hitting it.
- High Base Damage - Irelia has a really nice burst damage, which scales really badly with items. Getting a Trinity Force will increase your damage with a high amount, but afterwards, wasting 4000 more gold on damage items won't give you anything near the damage increase you get from Trinity Force.
- Mobility - Mobility is one of the things that Irelia does the best, and one of the things that makes her the best offtank in the game. Bladesurge is an ability that really helps chasing targets, and when maxed, it has practically no cooldown. Bladesurge would be enough as reason to call Irelia a really mobile champion, but riot have been kind enough to bless Irelia with Equilibrium Strike as well. Irelias Equilibrium Strike lowers the enemy mobility, and makes a really nice combo with her Bladesurge. The slow is even a stun, if your hp is lower than the target! When initiating, your target will have full health at first. The first Equilibrium Strike you use will usually be a stun. There's also one more thing that makes Irelia as mobile as she is; Ionian Fervor. Along with Mercury's Treads, most crowd control effects won't affect her too much, which is particularily good when someone with heavy cc is running away. All this mobility along with the three items that gives you even more mobility, makes her able to outrun pretty much every champion in the game. Also, once she's locked in her target, there's pretty much no way to survive.
- Lane Sustain - Ah, another of Irelias really strong points, laning sustain. Two of Irelias abilities along with her passive gives her excellent mobility, while to two others are for making her more of a solid laner. Hiten Style isn't really Irelias best ability, but it certainly does help you in the lane, providing health every time you hit something. Early on, the best use of this ability would be regaining health. This is, however, not really the best way of gaining health, since you'll be mostly just lasthitting them. Still it helps. What makes Irelia such a great laner isn't the sustainability gained through Hiten Sytle; it's the health you're going to regain from the ultimate, Transcendent Blades. During the recent patch, it got nerfed. The health gain from it got cut by half, but Transcendent Blades is still a good way to regain your health in lane. It won't actually be a free recall every 45 seconds of the game, but along with Philo's, Rejuvenation bead, and Hiten Style, laning as Irelia will be really easy. You'll be gaining around 50 health per 5, 8 from Rejuvenation Bead, 20 from Philo's, and the last ~8-15 will be coming from your base health gain. This way, you'll heal around 600 health per minute. Along with the 100~300 health from Hiten Style, and the massive amount of health you'll be regaining from your ultimate, you'll be regenerating pretty much all your health in just half a minute. This is what makes Irelia such a sustianable laner. Your passive will usually allow you to survive from 2 or even 3 man ganks, and heal it all back as soon as they're gone. You will have a lot of mana regen because of your Philo's, you'll be able to use Bladesurge on most minions that you'd otherwise miss. Also, it'll allow you to harass your enemy frequently. Most squishy champions won't be able to line with Irelia, espectially after level 6.
- Initiating Abilities - I'm not gonna lie, the whole initiating thing is Irelias weakest point when it comes to offtanking. The only proper way of initating as Irelia would be to just randomly Bladesurge something in their team, whatever gets out of position. You're most likely to get CC'ed, but your passive along with Treads would pretty much allow you to keep sniping targets, even if they have a lot of hard cc's. Still, I think there are other offtanks that initiate better than Irelia does, for example Jarvan.
So, I hope to have clearified why Irelia works so good as an offtank. She's really good at everything an offtank needs to do, and in some of the points she's simply the best in the entire game.
There are a lot of people that play Irelia as a DPS champion. There are a lot of reasons you shouldn't be doing this.
Irelias abilities doesn't scale well with damage. Your Trinity Force will give you a huge damage boost, but after buying two more huge DPS items, you'll barely see any difference in your damage.
Irelias DPS is used for bursting down squishies, not taking down tanks. Because of Irelias mobility, she can easily target the squishy enemies during teamfights. Those can easily be bursted down with just a Trinity Force (Other damage items won't increase your burst). Why waste this excellent mobility on trying to take down tanks, when your damage doesn't even increase by a lot when going damage items?
You can't do well in teamfights as DPS Irelia. You won't be an offtank when going more DPS items than just Trinity Force. If spending 8000-10000 gold on huge damage items, you won't be an offtank. And guess what, you can't play like an offtank if you're not an offtank! Try to get through the enemy team comp, you'll get killed. Try to focus down the tank, it'll take you ages to kill a tank as DPS Irelia, since you don't scale well. Even if you could kill the tank, you'll get killed. What would you do? Just stand outside and get in when everyone are down at 25% health?
Note: There's a difference between "having enough health to survive", and being able to tank Besides, when you think you have enough health to survive, it's only because their entire team isn't burning all their burst on you. If they realized they should counterplay you, they easily could kill you at once. There's no proper counterplay to an offtank.
Irelias Offensive Capabilities
Making something clear; your objective in teamfights is to tank the enemy burst, and shut down the enemy DPS by jumping right at their AD Carry and instantly bursting it down. This way, it'll be a really easy teamfight for your team. Since you should be tanking, you can't run too far away from your team, while you still need to make sure their carry goes down. Without any burst or a carry, you'll win the teamfight for sure.
There's something every Irelia player needs to know; what Irelia should and shouldn't be doing offensively. Irelia has a really nice burst with her skills, along with Trinity Force. Since you won't be itemizing offensively, you're going to rely on your burst to kill the opponents. You're not supposed to right click something and wait for it to die because of your awesome 500 crits, if you want to do that, go play an AD Carry. You're supposed to put all your burst on something, and instanty kill it or put it down to low health. If it's at low health, you will be able to catch up really quickly. Think of it this way, Irelia has a really nice burst, which would equal to most of her damage. Would you waste all your gold itemizing damage, so that your burst will be useless, or would you cut just a slight bit of damage, so that without any at all damage items, still do 80% of the damage you would if you'd build offensively? You don't wanna spend time trying to disable their carry, you wanna disable their carry. Try bursting harder by adding offensive items, and don't tell me AP Irelia works.
When it comes to chasing down enemies, this is what Irelia does best. Let's say an enemy is running away from you. You can't run too far away from the teamfight, since your objective is to tank as well. You burst their carry down to 20% health, and he lives. What now? Regret that you're not building DPS, and can't take down that 20% in one or 2 hits? Not really...
Their team will CC you, and the carry will run away. No probs, you have Mercury's Treads and Ionian Fervor. Once the CC is out, she won't be too far away. The Force of Nature and Trinity Force movement speed will allow you to catch up quicky. Even if he will be running faster than you, you have your Bladesurge every 6 seconds. Once you're there, you have your Equilibrium Strike, Randuin's Omen and your Trinity Force passive to slow him. You have your skills that'll finish him really fast. Imagine how fast you can kill something running away, then you'll be able to run back and start tanking them again, nothing will be able to run too far away.
Greater Mark of Desolation Greater Seal of Vitality
Greater Quintessence of Vitality
There are a lot of different viable rune choices, in the end I think it usually comes down to personal preference. I like to go Health /18 at both Seals and Quints. Why? Well, most of the usual rune selections are adapted for early game. I'm going to go through my thought process while picking runes, I'll explain why I've excluded many of the usually used ones, and hopefully it'll help you understand which kind of runes you should be using as Irelia.
Armor and Dodge seals are decent choices for Irelia, but I just don't find them as useful as some other people do. Why? Let's start off with the armor runes. Lategame, if their team is AD heavy, you'll definately have above 250 armor. If adding 13 armor to that, you won't find the results quite as useful as you might have hoped. The damage reduction won't increase with more than 1~3%. Early on is the only time when you'll find armor runes useful, and even then, the increased armor won't be too much.
At level 1, you'll be taking 27% reduced damage, instead of 20%. That means, for every 100 damage taken, you'll be taking 73 actual damage, instead of 80. That means you'll be taking 730 instead of 800 damage per 1000 "actual damage". 70 damage reduced per 1000. That's 35 reduced damage, which would just be a few minions attacking you.
From level 6 and forward, armor seals pretty much won't do anything at all. Instead of taking 30% reduced daamge, you'll be taking 36% reduced damage. Your HP will be around 1000 at that point, and you'll have 50 health regeneration per 5 seconds. The difference is that you'll take 640 damage instead of 700. At that rate, you'll be regenerating it in 6 seconds, without using your Ultimate or Hiten Style. Once you have your Warden's Mail, the insignificant damage reduction will be even more insignificant.
I wouldn't use armor runes for that small level 1-5 advantage, it won't actually save your life.
When it comes to Dodge runes, there's one simple reason I'm not using them. This is that it only blocks one type of damage, which is Physical Damage dealt by autoattacks. This kind of damage is really uncommon in the current metagame. Even the recent Ranged AD Carries have different kind of damage, which isn't just based on autoattacks. Also, even if autoattacking would be more common, the damage reduction is luck based, but that's just not my playstyle. During the average teamfight, you'll notice you won't be dodging many hits at all. Using dodge runes, in my opinnion, is only viable when going for Ninja Tabi along with defensive masteries.
The movespeed bonus after dodging a hit might be nice, but with a base movement speed of above 450, and the mobility that Irelia has, it's simply not worth putting even more stuff into her mobility.
Greater Seal of Replenishment Greater Glyph of Replenishment
Mana regeneration is not a good choice for Irelia, you just don't need it.
Your mana regeneration will be at around 30 mana per 5 once you have your Philosopher's, and that'd equal to around one Bladesurge which kills a minion every 5 seconds. Every 30 seconds, you'll almost be able to clear out a minion wave only by using Bladesurge. And how often does a minion wave spawn? That's right...
You won't actually be Bladesurging all the minions anyway, most of the minion kills will be lasthits. This will save your mana for other things, but my point is that you could actually afford Bladesurging every single minion if you wanted to. You do not need Mana Regeneration runes when playing Irelia.
The cooldown reduction runes are decent choices for Irelia, but I've decided not to use them for my build. The simple reason for this is that your cooldowns are actually really low, Bladesurge has a 6 second cooldown, and Equilibrium Strike has an 8 second cooldown along with a 2 second duration. 6 second cooldown spells wouldn't really be affected a lot, making that 5,5 seconds using CDR /18 simply isn't worth it for me. I'd rather have the Magic Resist.
Greater Quintessence of Desolation
This is really a good option for Irelia. Me not using Armor Penetration Quints is a personal thing, that a lot of people might disagree with. Early on, the damage difference if barely even significant, and even if it was a huge early damage boost, you won't be too agressive during the earlygame. Lategame, you won't notice the difference at all. The damage boost is simply too insignificanf for me to use these runes. I would rather have more health at 18. If you do the math, and extra ~140 health will allow you to block a real lot of damage later on. With a lot of MR, a caster might nuke you for no more than that 140 bonus health!
Again, Armor Penetration is a viable option for Irelia, I peronally just find the damaage increase too insignificant to actually use them.
The runes I'm using are /18 ones, and here are the flat alternatives. I'm not using these because, the /18 ones makes up for the difference at an early level. The ones making up for at the highest level would be the Magic Resist ones. And even at early levels, the difference isn't significant. Let's face it, you won't be tanking that much damage early on, and whatever you might tank, you'll heal back.
As Irelia, you'll notice that you'll usually be overleveled. Since you'll be farming a lot, you should be level 18 at the point when the enemy team is at around 11-15. The fast leveling, along with the whole -Before you're at a high level, during lategame, you won't actually be fighting anything- concept, I prefer /18 runes.
9/0/21 is today the most common mastery tree for Irelia. However, after a ecent patch, now that Irelias ultiamte is Physical, you don't need htose 9 in offense. Going 21 in the offensive mastery tree is pretty much useless, and Irelia isn't an exception. You get a little AD, an unsignificant amount of Critical Damage, all useless for Irelia. The utulity tree gives you extra experience, mana regeneration, buff duration, extra gold, movement speed, and more. The best players actually build the utility tree for AD Carries. What I have done is to take what I need from the Utility tree, and save the rest for offtanking. The cooldown reduction isn't really needed since your spells have low cooldowns anyway. The only disadvantage would be the movement speed, which is indeed useful. I do find the health from the defensive tree better though.
So, I've taken what I need from the utility tree, barely improved flash, and then put the rest into defense, so that I could get that nice little health bonus.
Not much more to say here, try it out, and you'll see whether you'll like it or not.
Ionian Fervor, Irelias passive, is certainly one of the most useful passives in the game. The cc reduction is not only useful during teamfights or when chasing squishy enemies, but also allows you to easily survive 2 or even 3 man ganks. Combine her passive with Mercury's Treads, and crowd control effects will barely affect you at all.
Irelias charging skill certainly helps her out a lot. It's Irelias main access when it comes to being able to disable enemies. Initiating with Irelia is usually done by Bladesurging one of their squishy keyplayers (Such as their ranged AD Carry), and start chasing her. There's no way to get away from an Irelia, once she's locked into you.
Bladesurge is useful for farming and harassing in lane as well, this is why I choose to max it first. When a minion is at low health, you can jump at it, reseting the cooldown, so that you can jump at the enemy right away and land an Equilibrium Strike.
Something worth mentioning is that Irelias Trinity Force passive is triggered by the jump, and used when damaging the opponent. It's just like charing in into an autoattack. The actual damage dealth won't be your AD + 140, but your AD x 2,5 + 140.
This certainly isn't the best skill for Irelia. It doesn't help her do her offtanking role, since the offtank DPS is based on burst, and the health regained from Hiten Style isn't too significant. Still, Hiten Style is a decent skill for Irelia. Although it doesn't help her do her role, it's a viable source from laning sustain. Early on, you'll notice last hitting will be easier with a skill point here, and you'll also notice how you might be able to stay at your lane a bit longer because of this skill.
This skill is one of Irelias most useful skills. It is part of Irelias burst damage, it's her only skill that does magic damage, and it even comes with a crowd control effect. You'll find this useful not only when chasing enemies, but also when initiating during teamfights or simply trying to deal damage to the enemies. Not many DPS champions have stun effects, we're all happy that Irelia has one (Right?).
Irelias ultimate... This skill certainly isn't the best ultimate in the game. Actually, it doesn't even come close. Irelias ultimate does deal damage to squishy enemies (assuming you're level 16 at the times they're 11~13...). It is part of your burst, and it does help you out. However, it barely does as much damage as your other skills. It's not a good source of burst damage, and at tankier enemies, the damage dealth is pretty insignificant. The best use of Irelias ultimate used to be to heal up on minion waves, but you can't do that because of the recent nerf, your ultimate now just heals 10% against minions. It used to be really great for lane sustain at level 11, and even at level 6. It does add a lot of lane sustain still, but doesn't come close to what it used to do.
In the end, you'll find this a decent ultimate, but no longer a reason to call Irelia overpowered by any means.
This is a basic skill sequence, although it should be adapted pretty often. Early game, you'll be farming a lot, and should max Bladesurge. For some early agression, you are offmaxing Equilibrium Strike. However, if you need more lanesustain and don't want to be agressive, you could offmax, or even max, your Hiten Style. If you are having a tough lane, maxing it is probably the best option. Play a couple of games and you'll know what you should be doing.
Exhaust: When offtanking, your objective is partly to shut down the enemy carry. Not only does exhaust prevent their carry fomr dealing damage, but it also makes him an easier target for Irelia. Exhaust is a great for teamfights, and since you don't need summoners to tank, why not use your summoners to shut down the enemies?
Ignite: Just like Exhaust, Ignite is to shut down the enemy carry. However, with ignite, you'll find some other uses as well. You won't always ignite their carry for an easier kill, sometiems your team will be struggling with some other champion which needs to be ignited. The true damage is great for hurting the enemies, but the healing reduction is great as well. Ignite also works great early on, and could get you some kills.
Pick ignite if you don't want to focus more on shutting down their carry, or if you feel like that's an easy objective as it is.
The times I pick ignite is when our team lacks it, and there are a lot of lifestealers in the enemy team. Otherwise, I personally find Exhaust more useful.
Flash: Really, Flash. This is the one summoner I'll always use as Irelia. Actually, I'll always use it as pretty much every champion in the game. Even though Irelia doesn't get killed easily, a misstake could easily cause your death. Flash is there to save you. Flash is not just a great escpae tool, but works great for ganking as well. Also, you can do great towerdives and such with Flash. Just a generally really useful spell for any champion. You should always be using Flash, then ask yourself whether you want Ignite or Exhaust.
Ghost, in my opinnion, is pretty much useless for Irelia. Why? You have your Trinity Force and Force of Nature movespeed buff. You sometimes have the Utility that gives you more movementspeed, you have your Bladesurge. You have your Stun/Slow. You have Randuin's. You have your Trinity Force slow. You even have your Passive and Merc's. You don't need Ghost to outrun anything, you'll be able to outrun everything with ease. You don't need to enchase your chasing with ghost, don't waste a summoner on it.
For Irelia, there isn't really a core item build. The items you'll be using will always be adapted to the enemy team, just like when playing any tank. Sure, there are a few core items fore Irelia, but once they're done, you need to start thinking of what you should be getting, depending on your enemy team.
This is what I usually get as Irelia. For starters, the Rejuvenation bead will give you some Health Regeneration which is needed. Early on, you will need some Mana Regeneration. This is why I don't start off just building Health. Your bladesurge will cost a lot of mana early on, you need some mana regeneration.
You'll get an incredible amount of health regeneration when building a Regrowth Pendant. Your philosopher stone will be cheaper as well, you can go back for it pretty much any time you want. If you don't feel like you actually need the Mana Regeneration, you'll find great use of this. I guess it comes down the personal preferance, early Mana or Health Regeneration.
Early Game Items:
Your early game is realyl important as any champion, and this doesn't conclude Irelia. It's the early game that determines how well you'll be doing your job lategame. In order to have a good early game as Irelia, you mainly need one thing, which is gold. The earlier you have a high amount of gold. the better. Your objective will be to farm, enough for at least a Trinity Force, as fast as possible. These items all help you do that, they help you farm up a nice amount of gold as fast as possible, allowing you to get your core item.
Philosopher's Stone: Philosopher's will be the first item you'll be getting, and you will usually have it after your first recall. It gives you all the mana you need to farm early on. It also gives you health regeneration, which is really great since it means you won't have to recall. If they leave you alone for half a minute after ganking you, you'll have your health back. Also, it gives you gold, which is good for building your Trinity fast.
Heart of Gold: This will be your second Gold per 5 item. Having 2 of these while farming the entire earlygame will give you a great advantage once you start teamfighting. And in order to offtank, you will need that advantage. Heart of Gold is a really nice item since it provides you survivability during ganks. If you'll get ganked, that extra health will help you a lot. This item is also builds into an item you'll probably be getting early on, and since it's so good early on, why not jsut pick it up the second time you recall or so?
Mercury's Treads: You don't actually need these early on, regular boots should be enough. These help you survive ganks, but doesn't do much more.
Sheen: Once your early game items are done, you'll be getting a sheen. This will start your process building a Trinity Force, while increasing your damage a lot. It won't really help you farm or get more gold, but it will help you keeing your opponent out of the lane; nobody lieks to lane agaisnt an Irelia with sheen, and nobody will once their turret is gone. You have a really strong early game at this point, and you have started building yoru Trinity Force.
Starting Defensive Items:
These will provde you a good amount of armor and Magic Resist, which makes you pretty tanky. Usually, once your Trinity Force is done, you'll be building these items (assuming your enemies have a regular team composition). As you might realize, which one you should build first depends on which of the enemies are causing most trouble early on. If you are having real trouble with a fed enemy early on, you can build one of these items before having your Trinity Force. Instead of QQ'ing about that fed AD Carry coming all the way from botlane to kill you, how about building a Warden's Mail and prevent it from happening again? It works, trust me.
Note: You don't have to build one of these at all times. If your opponent has a lot of magic damage, making something out of your Negatron before building a Warden's Mail is a good option. However, usually, the opponents damage will be disturbed between Magical and Physical damage, so that you'll need both of them.
Trinity Force will be your main source of damage. As already explained, you won't be building too much damage, and the Trinity Force will provide all the damage you actually need to be efficient as an offtank. Once you have it, you won't need to worry more about damage. Trinity Force also adds what you need to do well in the game; some Health, Mana, Movement Speed, and such. It also adds a really great slow effect. Trinity Force is really one of the best items in the game, and it's what every offtank is built from. Without Trinity Force, offtanks will pretty much be tanks with a bit more damage. Trinity Force is the reason you'll be farimgn so intensively, and the whole offtanking process is built of this item, at least for most of the offtanks.
Mercury's Treads is a great choice of item, these boots will provide not only really great sustain in lane, but will also allow you to work better as an offtank in teamfights. Merc's stack really well with your passive, I think I've explained the rest.
You'll have both of these most of the games you play. You'll have one of these every game you play. Once your Trinity is done, and you have your Warden's Mail and Negatron, you should be builing one of these items (Usually starting with Randuin's since you have your Heart of Gold as well). If the enemies don't have any Magic Damage, you won't have a Negatron Cloak and there won't be a reason to actually build a Banshee's. If they don't have any Physical Damage, you could sell your Heart of Gold instead of buying a Warden's Mail, and keep building Magic Resist.
Randuin's Omen: The reason this is such a great item is the fact that it doesn't only add a nice amount of HP and Armor, but the Passive and Active effect is great as well. For tankin g Physical damage, there simply isn't a better item than this.
Banshee's Veil: Just like Randuin's, this item adds HP. Along with Randuin's and Trinity Force, you'll notice having really high HP without actually 'trying' to build it. You won't be having any Mana issues, and the Passive isn't too bad either. Note that Force of Nature is a decent choice if you for some reason don't like Banshee's Veil.
At this point of the game, you'll be really tanky. You have your items that give around 300 Health each. You have an additional 300 health from your runes. You have your base Armor and Magic Resist, and the game might be over at this point. Look at your opponents team, where does their source of damage come from? Build towards that, it's pretty simple.
A little note is that, after you have a high amount of Armor or Magic Resist, you just won't need more. Once you have your Banshee's and Force of Nature, you don't need more Magic Resist. No matter how many AD Carries they have, building an Atma's wont' help you much when you have your Randuin's and your Guardian Angel. This is why Warmog's is an option during some games.
At this point, you will have:
3300 HP [Runes, Trinity, Randuin's, Banshee's]
65 HP /5
163 Armor [Randuin's, Masteries]
157 Magic Resist [Banshee's, Merc's, Glpyhs, Masteries]
You can buy 2 more items at this point, and you usually have 4 items to choose from.
Guardian Angel: Usually, you'll be having either this or Force of Nature as your first item. Guardian angel is a really good item, simply because it allows you to die. Simple as that, you can die. If you rush straight into the teamfight, kill someone, take all their burst, then die, you have done your job, and still gotten revived. This doesn't mean you should try to die, it just means you could die without being done. Usually, you'll select Guardian Angel when you feel like they have a lot of Physical Damage.
Force of Nature: When they have a lot of Magic Damage, Force of Nature will be your first choice. It doesn't just add a lot of Magic Resist, but also a nice movespeed buff which is great when taking down your targets. This is pretty much be your choice when you need to do better against Casters.
Warmog's Armor: After building either Force of nature of Guardian Angel, you'll either go for the other one, Atma's, or Warmog's. The times when I choose warmogs is when I feel that I don't need more than ~160 Armor or MR. If they don't have a lot of Magic Damage, I build my Guardian Angel, then go for Warmog's. If they don't have a lot of Physical Damage, Warmog's works once your Force of Nature is done. Against well build teams, you will usually be having both Guardian Angel and Force of Nature, though.
Atma's Impaler: Just need to make one thing clear; this isn't really an item you will be getting a lot. You don't need the armor from Atma's if you have your Guardian Angel, you'd be better off getting Warmog's if you need even more survivability against AD Carries. Usually you don't, and you'll be getting a Force of Nature. Don't get this item if you already have the Armor from Guardian Angel and Randuin's. Don't get this item instead of Guardian's Angel. The only times I actually get this item, is when I've itemized Guardian Angel / Warmogs, and Guardian Angel is at cooldown. I buy this item, and once Guardian Angel is off cooldown, I buy that again. If I have Guardians Angel / Force of Nature, it means the enemies have a pretty balanced damage output, which means you'll need your tankiness more than some more damage. There are times when you feel like you don't need the Guardian Angel at all, and then you could get Atma's, but usually Guardian Angel is a better choice.
I think I've covered msot parts of Irelias gameplay already. What you should be doing, how and when you should be doing it, how you should work during teamfights, and so on. Still, I would like to make clearify your exactly how you should play as Irelia, from early to lategame.
Clain solo top. In order to play Irelia properly, you need to solo top. If someone else wants it, pick another champion. If you don't have a jungler, pick another champion. Simple as that.
Before level 6, Irelia is one of the weaker champions. She lacks lane sustain and is very vunerable to harassing. At this point, you should be playing as passively as possible. You don't need to farm that much before level 6. Just make sure you won't die, and don't let the enemy damage your turret too much. If you find yourself being level 6 without having a death, you've succeeded.
Once you reach level 6, laning dominance begins. You'll be really strong in lane, and have great lane sustain. And squishy enemy will be scared of coming anywhere near you, your range is really long and your damage is high as well. Whenever you have your ultimate, you'll have a really easy time regaining your health (although the ultimate is no longer the best way to regain health as Irelia). Sometimes you'll be able to zone you opponent, preventing creep kills or even experience. Somtimes you will have to settle with just farming up yourself, and in some very rare occassions even your farming is limited. In either case, your main objective will always be to farm. Farm, farm, and farm. Since being an offtank requires a lot of items, you need to be at least as farmed as the enemy AD Carry, and prefeably a couple of levels ahead as well. If you're up against an enemy that's a lo t below your own bracket, you could go for the kill. You don't actually want to try to kill him, and you're not going to need your jungler in your lane.
You usually won't need to recall because of your health regen, but once in a while you should be recalling to get items, espectially before you get your early game items.
Try to stay at your lane as much as possible. If your enemy goes down, you shouldn't follow him unless you're needed to prevent deaths.
After around 20-25 minutes into the game, you'll be done farming. You will have your Trinity Force, and some of your defensive items. At this point of the game, you'll be really strong. You will be ahead in levels and in creep score, and you will probably have an advantage in teamfights. You don't actually need to play passively anymore. Usually, you should try to get as many teamfights as possible at this time. You won't be as tanky as your tank quite yet, but you'll still be able to tank some of their damage. What's so good about midgame Irelia isn't her tankyness, it's her damage. Burst damage is more efficient early on, and in Irelias case it doesn't improve for the rest of the game. You're overleved, but that advantage will end soon. Try to take advantage of this. You have a really easy time to use yoru advantage, and make the gap between you and your enemy team even larger. Play pretty offensively, although how you'll be playing will vary depending on the situation. After a couple of games, you'll know what you can and can't do as Irelia, and you'll find it easy to adapt.
The lategame isn't really Irelias strongest point, although she does a great job offtanking. The difference between lategame and midgame as an Irelia is that you can't single handedly carry your team anymore. If you did really well during midgame, you may have kept some of the advantage or even won the game, but this isn't the case in too many games. Usually, you'll have the same damage as during midgame, and the enemies will all be tankier. You won't be able to kill everything really fast, although squisheis will go down pretty fast anyway. So, the positive difference between midgame and lategame as Irelia, is that you'll be a lot tankier. You can't kill them all at once, but you can kill the sqishy enemies, and you can tank everything really well. Even if your carry isn't too farmed, it should still be pretty easy to kill things since you'll keep the enemy team busy for really long. Basically, go rambo, do your job, and play Irelia just like you'd play any other champion outside teamfights.
I guess I've clearified what Irelia should be doign at certain points of the game, although I havn't gone through exactly what should be done. Irelia is played like any other champion, your gameplay stratergy won't change. If you do dumb things, you'll do dumb things. Which champion you're playing won't matter.
This is just a summary of Irelias strenghts and weaknessess, and how your game should be played. If you're bad, you need to work on your general gameplay, not your build or your playstyle with a particular champion.
There's no proper counterplay to an Irelia that's building offtank. You can't cc her, you can't run away from her, and you can't kill her.
This is different when it comes to DPS Irelia. You can simply focus him down really easily.
There's definately more to the whole counterplaying concept, but after hundreds of games as Irelia, I havn't actually been counterplayed in a way that I can't offtank although I'm farmed. The best way to prevent an Irelia is to prevent her from farming - thus prevent her from becoming an offtank.
If you want a proper way to actually conuterplay Irelia, you've came to the wrong guide. I can't really find a way to coutnerplay a properly built Irelia, although there should be ways.
Well, this is the end of my guide. I hope that everyone who have read through now have realized why offtanking is as efficient as it is, why Irelia is such a great offtank, and why it's a waste to play DPS Irelia. In the end, a guide won't have you properly understand this. Before you've actually seen the difference between an offtank and a DPS Irelia, you might not understand the difference. Still, I hope you'll all be open minded to offtanking rather than playing DPS - there have been a lot of missconceptions regarding how to play Irelia (There's a difference between "having enough health to survive", and being able to tank Besides, when you think you have enough health to survive, it's only because their entire team isn't burning all their burst on you. If they realized they should counterplay you, they easily counld).
Any constructive critisim about anything in this guide is appreicated, positive as well as negative. I'm open for suggestions to improve this guide, and the way I play Irelia. Open for all critisim, don't be afraid to leave a comment. I won't flame anyone for not sharing my opinnions.