Pros:
- Can build very tanky and still assassinate carries.
- Very hard to peel from carries with her extended tenacity.
- Good sustain even with the heavy nerf.
- True Damage ^_^
- Farms Easily, including under tower.
- Great scaling, especially into Mid Game.
- Has no true hard counters (Not even Olaf or Jax)

Cons:
- Squishy early game.
- No hard escape.
- First few levels are not very strong.
- Can go OOM (out of mana) early on.
- Gets nerfed too much.
- Generally doesn't hard counter anyone.

So, Season 3 is here and we have many new items, and many of the old ones have been changed. So why these items?

1.Mercury Treads: To be honest, while this used to be core on Irelia because it stacked with her passive Ionian Fervor, you already get tenacity from Zephyr, making the tenacity on this item rather useless. This item mainly exists in her build right now as some bonus magic resist, because the only other item that gives magic resist in this build is the Runic Bulwark . Feel free to change these for other boots, including Berserker Greaves.

2. Zephyr is one of the new Season 3 items, and wow look at the stats! 20 AD, 50% AS, Tenacity, 10% Movespeed, 10% CDR. All of these stats benefit Irelia in some way, especially the AS and Tenacity. It is a bit expensive, but it synergizes with her kit (particularly her Hiten Style) so well that I would consider it a good buy most of the time. You can substitute Wit's End for this item which is perfectly acceptable too though.

3. The Randuin's Omen was arguably one of Irelia's core items in Season 2, and I'm willing to say it still is. While the active does not reduce attack speed anymore, only movespeed, the passive reduces attack speed by 20% and movespeed by 10% EVERY SINGLE TIME! This item not only offers a pretty good amount of health and armor, but the passive makes it that much difficult for that pesky Vayne or Ashe to kite you while you try to kill them. Getting an early Warden's Mail in lane makes auto attackers a joke to trade with (assuming you haven't fallen too far behind), and even now, the movespeed slow on the active is strong for chasing, just not as strong as before.

4. Tons of Damage is what you want to do to carries, and this item is what that will make you do that. Just like Season 2, this item is still a great item for Irelia despite the mild nerfs. It offers sustained damage through the AD from Phage, as well as the slow, and the raw health is never bad. The mana is good because Irelia can run out of mana especially early if she spams Bladesurge too much early game. The AP is not particularly helpful, but it makes up the other half for Sheen. The passive is excellent because her Bladesurge applies on hit effects, including the Sheen proc. When upgraded to Trinity Force, a Bladesurge can kill caster minions in one hit during the mid to early late game, so abuse it. Lastly, the attack speed from the Zeal synergizes with her true damage from Hiten Style , and the movespeed also helps with Irelia's strength to control and stick to single targets - carries. Trinity Force can often be built later, although an early Phage is almost always a good idea. The sustained damage and health helps her in trades and survivability, as well as when the minions get more armour to last hit under her tower.

5. Yes, Runic Bulwark. Now you might say it is a support/jungling item but look at the stats it gives. 400 Health, 30 Armour, and 60 Magic Resist. The most MR item in the game currently, and that alone is enough to get it. Getting an Aegis midgame is optional, but this item offers so much resistance to magic damage and some armour and health that it is quite a good item, especially with the Guardian Angel nerfs. By late game, where AP Carries fall off, especially with the recent nerfs to Magic Pen, you should be able to survive most AP Carries.

6. Lastly, the Frozen Heart. This item was in my honest opinion, ridiculously overpowered in Season 2. Nothing really countered attack speed reduction in the form of a constant aura, and even with the nerfs, it's still very strong. 90 armor, 20% CDR, 400 mana, and an attack speed reduction aura. The reduction stacks with the Randuin's, making it very very tough for ad carries to do damage to you with all the armour, and if that wasn't enough, their attack speeds would be greatly reduced as well. Very strong item on many tanks/bruisers, especially those who can get in the center of the team, like Irelia.

1.Wit's End. A definite core item on Irelia in Season 2, and I would still consider it to be one of them in Season 3, regardless of the 10 magic resist nerf. It synergizes ridiculously well with her Hiten Style, and provides her a pretty good amount of magic resist, and the extra 42 magic damage really adds up with the attack speed. Of all the items, if you were to replace one in the build I mentioned, this would be the item you would most likely want to sub in, because it is so good on her. Generally I would substitute Zephyr for this item, but I would usually only do it if I am against an AP top like Vlad, as while admittedly it gives a huge increase to your dps mid game and generally mid game is where AP Carries are strong, it holds back armour items if you are against an AD top, which is usually the scenario.

2. Guardian Angel. I would say this item is generally core on most bruisers, but the nerfs to it have made me dislike this item. It's still a good item, and offers a balance of armor and magic resist, making it good on offensive oriented bruisers like Riven or Jax. Irelia in a way is offensive in how she can easily kill carries with the (almost) immunity to CC that she has, but itemizing her very tanky is generally the way to go, as she really only needs a few damage items to hurt. The stats on GA are in my opinion, just not good enough when compared to items such as Runic Bulwark, or Randuin's Omen. If you want to get it, go ahead though, it's still a decent item on her, even with the nerfs.

3. Alright, Atma's. This along with Warmog's, or Frozen Mallet is a very common build on bruisers, despite the many nerfs to this combo. It creates a niche "I build tanky and still do damage), but this combination doesn't fit Irelia as much as other bruisers, because she scales off of Attack Speed better than AD. This combo is alright on her, although it doesn't provide the same kind of armor that Randuin's and Frozen Heart do. It does give a good chunk of health and potentially some AD though, although i would not usually get this on Irelia. Feel free to try it though.

4. Speaking of Frozen Mallet, this item can also be part of your build on Irelia, usually replacing Trinity Force. The recent buff that gave this item 10 more AD in my opinion is good enough to make this an acceptable purchase in place of the Trinity Force. It doesn't give as much damage overall, but the consistent slow it provides is unmatched. It may be a bit overkill considering with full CDR, you have great single target chasing potential, and the slow from Randuin's active and passive. It is still a good item on her regardless of this though.

5. Wriggles. In Season 2, this item was alright top if you truly wanted lane dominance or if you needed the extra armour and sustain it provided, as well as a free ward. The only problem is that this item has very little scaling into late game, and sets back your core items by a significant amount, so unless you really needed it to survive in lane, it was generally not as great of an item. In Season 3, it was nerfed a fair bit again, so I really try to avoid getting this item. If you are losing your lane hard, a Philosopher's Stone would help a bit too. While the sustain got nerfed, Irelia alone has some pretty good sustain herself, despite the nerfs. Avoid this item if possible, but I would say it is still acceptable.

6. This item is really strong right now, and I would say it is a very good item especially on AD Casters like Riven or Talon. While Irelia isn't exactly much of an AD Caster, she makes use of the Flat Armour Pen as her job is to kill carries, and the Armour reduction works well with the fact that she generally builds attack speed. The CDR and health both benefit her as well, and the chunk of AD is also quite nice. Substitute for Trinity Force if you like this item, but Irelia needs attack speed, so avoid getting rid of Zephyr or Wit's End for this.

Ignite: Very good spell on many champions, and does some good extra damage, as well as ruin lifesteal and help get kills early on in lane.

Flash: Great spell for a lot of people as well, but great on Irelia because she has no hard escape, and if you are setting up for a gank/in teamfights being able to flash stun is absolutely amazing. Irelia's Equilibrium Strike's stun is based on whether or not you have less HP percent than your target, and if you are both full health and you Bladesurge into your target, you won't get the stun you want.