I'll Start off by saying Irelia is probably my favorite champ in the game, and this build works great with her. The reason Irelia is so good at mid is because of her ability to jump at enemies with BS and gain back health with HS and TB. Also, most of the time you will have a health and strength advantage over the usually squishy mid champs. Through out this guide I will teach you how to use these abilities to rape.

FOR THIS TO WORK WELL YOU MUST GET MID

For summoner spells I like to go with and . I find teleport to always be useful when going mid, because it helps you get back to mid without wasting time. The second summoner spell I choose is ignite for help getting that first kill. At first your only going to be doing a little harassing, so when lvl 3 comes around you want to make sure you get the kill, and get it quick. I also find to be useful to make sure you can chase down anyone, or for an escape, but I don't find it necessary because you get boots of swiftness.

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Mark of insight is great because of the starting magic penetration. Seal of alacrity give you extra attack speed which is always useful for physical dps. Glyph of Celerity's cooldown reduction is manly useful for your ult. This allows you to cast your ult so frequently that there entire team will rage quit. Lastly Quintessence of fortitude is probably the most useful of them all. The extra health from the Quintessence really helps you stay in your lane longer, and get that first blood.

Bladesurge: BS is the ability that to me allows Irelia to go mid. BS allows you to jump at your enemy and hit them for a bit attack damage. This is useful because at mid you enemy is usually ranged, so this gives you a opportunity to get near them and do some real damage. This is your initiator, and combo starter.

Hiten Style: HS is extremely useful because it allows you to stay in you lane much longer than usual and the extra true damage helps you dps tanks.

Equilibrium Strike: ES is another ability that is very useful for mid. After jumping to them you have a chance to stun allowing you the opportunity to do lots of damage. However if you have more health then them it will slow them which still allows you to chase them down.

Transcendent Blades: TB is (in my oppinion) one of the best ults in the game. It is extremly versatile. The fact that it is a skill shot that goes through minions is very useful because it gives you a ranged attack for harrasing, TB is lifesteal so it gives you health back and allows you to stay in ur lane longer, it can take out entire waves of minnions for pushing, AND it has a pretty low cd.....what more could u ask for.

I've tried out a few different things and this seems to work the best. It allows you to stay in you lane longer and goes towards your next iteam.
Sheen was made for Irelia. Lets think about it, after using BS to jump to your enemy, your next attack does 80% more damage.
First off, the idea to use this iteam comes from P.DiddyXD. This is such a great iteam for its cost. You get some ad, magic resistance, and a great passive. The passive pretty much absorbs 300 damage from a spell that would kill you when your at 30% health.
You will realize early on that the job of Irelia mostly consist of chasing ppl down, so the slow from phage is gonna be great, also the health helps towards your survivability.
This is the item we have been working to build. Once again, a great item, especially since it uses 2 items that we already needed to make it. It is also a very well rounded item in general.
Our last main survivability item is guardian angel. Just a back up at this point since we are gonna be doing a lot of initiating and diving.
These last items are pretty changeable based on your style and how the game is going, but the extra speed is gonna help you get health back quicker and just in general help you dps.
Bloodthirster is a good late game item for its extra life steal, also this will give us some ad for our abilities.
This is gonna be our final item and is pretty essential since tanks are gonna start becoming a bit harder to kill. Highly recommended but there are other items you can choose based on your situation.

Early game

Start off getting your crystal and head to mid. If you don't get mid then please stop reading. Ok moving on. Get 1 point in BS and begin assessing your situation. If your enemy has slows and stuns like Ashe, be a little careful with your harassing, otherwise feel free to jump in using BS and then back up so minions don't attack you. If you are new to Irelia and not quiet used to her yet, then wait till lvl 2 when u have ES also. Once you have ES let them weaken u till you are just below there health and then start jumping in,stunning, backing up while they are stunned, and repeat. Continue this till you are worried your health is to low or until you can kill them. Once you are lvl 3 you get HS which you can use to get health back off minions if you think your to low, or use in your newly gained combo BS>ES>HS feel free to throw in an ignite to get that first blood. You shouldn't be to worried about health since you have 2 health potion and a passive lifesteal.

Mid Game

You should be lvl 6 now and have at least your sheen and maybe your boots. If you have had trouble getting any kills or even harassing, have no fear, because now you have your ult. This is gonna once again let you stay in your lane but now u can start harassing from a range. As you level, start going around and helping your friends using your ult as frequently as you want. It should be pretty easy at this point, all you do is continue to use your combo, or if your in a standoff where you don't want to jump in, use ur ult. Just sit back and feed till late game.

Late Game

By now you will be at different points each game, ur probably about lvl 15 and have a guardian angel or trinity force. I really don't have much to say at this point. You just continue on your path of rape. Usually you wont need to worry about health anymore with your lifesteal and ult. Best part of late game....watch the ragers rage =D

As of right now my only other tip is to switch lanes if their mid is Kassadin, his silence will wreck your combo and your anus.