So i think i must to do a introduction, but no one cares about it so i will not do it.
But how you see, my gamestyle is very weird maybe.

So let's talk about masteries.


Wanderer will give you more speed on map when you are not in battle, this allow you to raom better and return faster on lane, is not a bad choice, but in my opinion Savagery ] is a better option cause allow you to farm better.

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Runic Affinity nah
Secret Stash a good option to stay longer on lane, you really have no reasons to recall before have enough money to buy gunblade
assasin will give you more damage when are solo on lane, but is really useless in teamfights

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Merciless good to secure the kill, will give you 3% more damage on low hp enemy.
Meditation i don't think i must say why this is a bad choice

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Precision will give you some lethality and magic penetration, and this is very good cause katarina use and ap and ad damage from passive.
Intelligence cause of the passive this will be very usefull in a team fight, but you can choice it to reduce more the cd on ultimate.

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Thunderlord's Decree is a standard keystone for mages, this work good and on katarina , sometimes anyway i use Deathfire Touch
Stormraider's Surge again i see like a bad choice, katarina is very mobile and can catch eveything anyway, i will say later about it.

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Sorcery and Fury not need explications, ap > attack speed

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Fresh Blood good if you want to to a lot of trades except q>e>e and stay and to do some basic
Feast will give you more sustain in lane and this is good cause you need to stay very longer
Expose Weakness can be good for your team, but we will be selfish, team must help you to get a kill, not you help team to steal your penta. K just joking, but i really think this is a good option for support not for an assasin sexy.

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Vampirism Gunblade will give you all you need, you really don't need it.
Natural Talent a good choice, cause katarina players are a natural talent ^.^

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Bounty Hunter this is the goodest option, i will not talk and about it, if you prefer Double Edgde Sword or Battle Trance nobody will stop you to choice it.

So let's talk and about the weird items we choices.
k are you ready, okey.
Hextech Gunblade a.k.a i will steal you life is core item for katarina, this sustain you a lot in fight and his active will grant you a kill.

Okey now i must start talk about first weird thing you seen in guide, and this is start items. So, Katarina alerdy have a lot of damage, this allow you to start safest with Cloth Armor or Doran's Shield versus an ad champion like zed/talon or someone who do a lot of basic attack (kassadin, fizz). Maybe is wrong but this work eveytime and will give you enough sustain to can resist and maybe defeat him very early.
Now if you want rush Hextech Gunblade from start, just buy Long Sword and few potions, and this could be a mistake, i not say is not, long sword start item really is a mistake.

Now let's talk about other weird item and try explain why you must buy it and when you must buy it, and this is Adaptive Helm. Now let me explain, [[Adaptive Helm] is a great item versus mages who just spam spells every time, like cassi, ryze or teemo, and will give you a chance not just to survive, but to kill they, except teemo, you kill teemo and without it. Now qss you must buy only when your enemy have a hard cc. I don't really remember why i added and spirit visage..

Flash is a standard spell
Ghost you alerdy are very mobile
Ignite Good to secure the kill
Barrier and Heal your E always will help you to escape, you need just an ally, or any minion of the map, or a knife, you don't need a spell to defensive, anyway you will have zhonya.
Smite katarina jungle new meta?
Teleport easiest way to roam

i'm to lazy to explain so the easiest way to both of us is to show you few combos. Play Video

Do not forget to leave a feedback about the guide and if this helped or not you.