Warwick is an exceptional character even after his many buffs and nerfs over both seasons. Beginning as one of the first amazing junglers, Warwick has been adapted in playstyle to be played top lane, mid, or his original home, the jungle. This guide will show you how to use Warwick in a way that will make kids mad, will make you unkillable in most circumstances, and be able to carry a game single-handedly.

Remember that whatever you play him as, or wherever, you must adapt your playstyle and build to reflect your opponent. Therefore, this guide will go over the many ways to adapt Warwick so that he can carry you in any situation. Here is the Beauty is the Beast:

Magic Resist Flat or per level Blues
Flat armor Yellows
Magic Pen Reds
Flat health, Flat Armor, or Magic Pen quints

Warwick's skills stay relatively constant no matter the opponent due to the sheer damage and utility of his Hungering Strike (Q). Maxing Q first will give you high sustain and damage early, possibly enough to force your opponent to go back or give up first blood. Obviously take ult points when you can, as this is what makes Warwick useful mid and late game.
After that, you will have to choose between W and E. E gives speed and awareness while W gives increased dueling capability. I will usually go E first because often times I will forgo buying boots at spawn and go dorans ring or armor/mr. Having E on early will make your harassing scarier and your ganks more successful. W can be good however if you're against opponents that duel often, such as Fiora, Olaf, and Wukong. Having the boost to AS and your Q available will ensure that you come out of any duel the victor or nearly even.

First: Doran's Ring, Boots + 3pots, Cloth Armor + 5pots, Null Mantle Cloak + 2pots

Some opponents will require different starting items to counter, so pay attention to their lanes and jungler. If they have a good jungler or have a lot of cc, get boots. If you don't expect a visit, grab doran's. If they play an AD carry top or strong AD character, grab CA and pots. Vlad or Rumble top, or nearly anyone mid means grabbing a Null Mantle or boots to dodge abilities. Remember, you can't sustain your way out of a bad match-up if you are getting nuked every couple seconds. Getting protection early means you will stay near full health and you can save mana for attacking your opponent.

First Comeback: Merc Treads/Sorcerer Shoes and Mana/CDR item (Glacial Shroud or Chalice of Harmony)

The first time you go back, hopefully with 800 to 2000 gold, grab either a Glacial Shroud (against AD opponents), a Chalice of Harmony (against AP opponents), and Level 2 boots. With these items, you will take far less damage and will enough mana to spam your Q and Ult whenever you need it. CDR means more damage output for Warwick, that's the key to being successful, so items like Glacial Shroud or getting Blue Buff make a world of difference for him.

Note: Sorcerer shoes will give you even more early game damage since base MR is pretty high. However, late game will be tough if you are chasing a lot without Merc Treads. Depending on how your opponent builds, this may be a tough decision.

Second Comeback: Possibly Spirit Visage, Wit's End

Spirit Visage will increase your sustain dramatically and your damage output. This item is great on Warwick because it lets him exploit the benefits of playing him even more. MR for protection against AP top or mid, CDR, and increased healing.
Wit's End also gives great protection and works stupidly well with Infinite Surpress. 42 damage per hit 5 times plus his regular base damage is a lot considering you haven't even built AD on an AD stacking ult. This item also makes your W very useful for dueling and clearing creep camps.

Third Comeback: Finish Frozen Heart (if their AD carry is doing well), Banshee's or Quicksilver Sash (if their Mid or AP top is going well)

Alternatively, these items can also be very useful on Warwick:
Zeke's Herald
Randuin's Omen
Madred's BloodRazor
Guardian's Angel

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Expanded Mind and Meditation in Utility

Go right down the second lane in Defense, only with 2 pts in MR and 3 pts in Armor. Also, I use Tough Skin and Bladed Armor for both jungling and the lane.

Summoner's Wrath in Offense

Take Flash and Ignite in nearly all cases. Q + Ult + Ignite + Q combo will kill everybody other then tanky tops like Shen or Cho' Gath. It will also be useful in case you duel against a lifesteal/healing champion life Olaf, Irelia, or Mundo.

Ghost and Heal are useless because you have them both built into Warwick already. Teleport should never be used as you should have no reason to use it other then ganking other lanes. All the other abilities are irrelevant.

This set-up gives Warwick the ability to not die, kill other people, and be influential in team fights. You are tanky, yet do tons of damage over time. Your ult will force people to attack you, which protects your carries as they kill the whole enemy team which has yet to kill you. Seriously, playing a nice and tanky Warwick is like beekeeping, and the enemy team are the bees. You just go in there and do whatever you want to them; they will sting you all they want but it won't do anything. You just Q someone down to half health and walk away like its your own ****ing map. And that's because it is your map: Warwick used to be King of the Jungle, but now he's King of the Lane. Deal with it........