Pros:
-Insane Burst
-High Mobility (Great Roaming)
-Strong Mid-Game
-Fun to Play
-Attack On Everyone Ultimate
-Snowballs when ahead
-No mana
Cons:
-Squishy
-Very hard to play and master
-CC can be a problem
-Falls off Late-Game

Flash: This is the standard spell for anyone besides Vladmir, Olaf, and Singed, who don't always take it.

Ignite: The wonderful provider of first bloods, cheap kills, heal prevention, burst damage, and so much more. I feel like I'm selling you all a product, well I guess Ignite is officially a product, used mainly by assassins or aggressive non-junglers.

Barrier:
I've actually seen this work form time to time, however it doesn't work even close to as well as [ignite], though it has a shorter cooldown. It is perhaps a good summoner spell for beginners to League of Legends who are trying out Katarina

Exhaust:
Don't take this. Even versus Assassins.

Ghost:
You have enough movement speed and you have your blades to move around quickly.

Heal:
What are you taking [heal] for, you are an assassin...

Teleport:
This is counterintuitive with your kit. You are going to be roaming without this, you don't need it at all, you can just walk to lanes, jeez, don't be this impatient.

Cleanse:
I mean I guess I could see this being taken if 4 or 5 champions on their team have extremely hard CC, eg. [orn] top, [Malzahar] mid, [sejuani] jungle, and a [varus] and [alistar] botlane.

Smite:
Now don't be an idiot, we both know that smite is ONLY for jungling.

Domination:

Keystones:

Electrocute- We take this because it is strong for bursting people down and works well for first bloods. We want damage, and this provides just that.

Predator- We don't want predator because we don't need extra MS and we much prefer additional damage

Dark Harvest- This is a cool idea, but it takes way to long to stack up, so it doesn't help us when we need it, which is during our midgame power spike

Cheap Shot- We don't impair movement or actions at all. Useless.

Taste of Blood- It is an interesting idea, but it doesn't add up to as much damage as sudden impact. If you want to play more like a Cassiopeia try this out.

Sudden Impact- Your E is a blink, this adds damage to that. It also gives a burst when leaving stealth, which is exactly what we intend to do when we go to kill people.

Eyeball Collection- Works well for our Mid-Game spike, and besides Zombie Ward has been nerfed, and Ghost Poro is next to useless.

Ghost Poro- It's cute, but useless because people can just scare them out of the bushes and it's simply not worth it.

Zombie Ward- When this got heavily nerfed it only continued to see play by the pros because they know how to properly utilize it, and take advantage of amazing vision.

Ravenous Hunter- It's actually a cool idea, but we would rather have CDR but if you are interested in trying a more lifesteal build you could choose this and Taste of Blood

Ingenious Hunter- Better then the alternatives as we value CDR over out of combat movement speed and lifesteal.

Relentless Hunter:

This actually also works, I think the Hunter Rune category is personal preference for Katarina, because some people might want the additional MS that this will give for roams. Ultimate Hunter: This could actually be an alternative to Ingenious Hunter because we can get up to 15% CDR on our Ultimate which is most of the reason we want CDR. I just haven't tested it out, but it looks to be pretty viable.

Resolve: Bone Plating- This is so ridiculously good against just about anyone in lane, and pretty good outside of lane as well. Extra armor means living for longer, which means more damage. Second Wind: Can help us sit back and farm with our Q while recovering with this and sometimes Doran's Shield

Passive Voracity-
INNATE: Whenever an enemy champion dies within 3 seconds of Katarina damaging them, her Cooldown reduction icon cooldowns are reduced by 15 seconds.

Sinister Steel
SINISTER STEEL: Whenever Katarina retrieves a Dagger, she uses it to slash through all nearby enemies, dealing 68 - 240 (based on level) (+ 100% bonus AD) (+ 55 / 70 / 85 / 100% AP) Ability power magic damage and reducing Shunpo Shunpo's Cooldown reduction icon cooldown by 78 / 84 / 90 / 96%.

Daggers last 4 seconds before disappearing.


This is where all of our late game damage comes from. It is also what Katarina is based around, if you are able to properly maneuver and set them up.

Q Bouncing Blades-
ACTIVE: Katarina throws a Dagger to the target enemy that bounces to up to 2 nearby enemies, dealing magic damage to each target.

MAGIC DAMAGE:
75 / 105 / 135 / 165 / 195 (+ 30% AP)
The Dagger then lands on the ground 350 units opposite from where it struck the target.

The time to land from striking the target is the same regardless of distance traveled.
This ability is a fun one and there is a reason we max it. We can bounce this off of minions or off of champions in lane to set up daggers for Shunpo. It can do a bit of damage, but the main purpose is the blade.

W Preparation-
ACTIVE: Katarina tosses a Dagger into the air above her current location and gains a decaying Movement speed icon bonus movement speed until it lands after 1.25 seconds.

BONUS MOVEMENT SPEED:
50 / 60 / 70 / 80 / 90%
Chasing someone down? Use W. Want to dive or go in on an enemy in lane? Use W. It can give u good AOE damage in teamfights as well.

E Shunpo-
Katarina moves to her target's location, appearing behind it. If the target is an enemy, she deals 15 / 30 / 45 / 60 / 75 0.5 total attack damage 0.25) magic damage to the target. If cast on a dagger, or walking over one refunds 78 / 84 / 90 / 96% of Shunpo's total cooldown.

This is the essence of Katarina, it is how you outplay opponents, how you escape and stick with champions, it is your everything. It allows you to have insane mobility, whilst allowing for strong lane all ins and engages

R Death Lotus-
Katarina throws a flurry of blades, channeling for up to 2,5 seconds and sending up to 15 daggers at the each of the 3 closest enemy champions dealing up to 375 / 562.5 / 750 (+ 3.3 per bonus attack damage) (+285% of ability power) magic damage over 2 seconds to each champion. Daggers that are thrown apply Grevious Wounds, reducing healing and regeneration by 50% for 3 seconds.

Insanely busted as long as you don't get CC'd you will be able to get a lot of damage. AS SOON AS THEY LEAVE IT YOU NEED TO CANCEL IT AND FOLLOW UP. This is the only way to be able to maximize your damage because otherwise you're just sitting there doing absolutely nothing while waiting for the full channel.

Dark Seal

vs.

Doran's Shield

These 2 items are the only 2 starts that really have success, I have found Long Sword simply not to be as effective. Dark Seal start is a popular start on Katarina as it provides extra healing from potions(and more Health Potions), along with having better snowball potential due to additional stats. The Doran's Shield start is also a safer option, that still allows for aggressive play. I have found that you should start Dark Seal in matchups where you know you can dominate them. The Doran's Shield is safer and more reliable, so it is especially good for those learning Katarina due to it giving additional health, health regeneration, and even extra damage to minions, which is useful when last-hitting.


Hextech Gunblade:
This is the single target burst damage that every Katarina main yearns for. AP for abilities, AD for auto-attacks, and a active that does a bunch of damage. It does more damage then Hextech Rocketbelt and provides us with the stats that we want. It is always our first item and is usually completed just after level 6.

]
Sorcerer's Shoes:
This is where our first MP comes from and it helps us eliminate all basic magic resistance enemy champions have while providing us with good mobility, I sometimes complete this before Hextech Gunblade if I have 1100 (or 800 if you start Boots) gold on first back.


Ninja Tabi:
If you face a team with 4/5 AD champions this is a worthwhile purchase, a rare buy for Katarina though it can be helpful when it used properly.


Mercury's Treads:
These are what allow us to still burst down champions who are protected by heavy CC and peel compositions, they are often a good buy vs. teams with high AP burst alongside strong CC.


Morellonomicon:
This is our lovely healing prevention, which happens to also provide some magic penetration and tankiness. With this we can survive for longer while pumping out loads more damage, I have found myself getting this as my second item more and more often due to the resurgence of Dr. Mundo, Soraka, and Vladmir in the meta.


Rabadon's Deathcap:
The AP champions item. This is simply all we want as an AP champion so long as we have our other AP items this can be a good 3rd item, though it also works as a 4th one.


Void Staff:
This is an item we like to purchase early on in our build because it provides us with the proper magic penetration to begin really bursting down carries, I have been starting to use this over Morellonomicon as it has a better effect on the game due to the damage output.


[[Zhonya's Hourglass]:
This can be bought vs. Champions like Zed or Fizz who have ultimates that you can use it to dodge such as, Chum the Waters. It can also allow you to survive in precarious situations and to dive into a team and come out of it alive because it gives your team a little bit of time to engage.


Spellbinder
This can basically guarantee that you kill the carries because of the great amount of damage it provides you with. When used properly it can allow you to simply kill the backline guaranteeing a win in the fight.


Banshee's Veil:
This can help to allow you to survive burst from behind or against fed or overpowered burst AP champions. It also provides a large amount of AP for a more tanky item.


Mejai's Soulstealer:
If you know you can kill everyone and not die this will basically guarantee that you can clean up the whole enemy team, you have to be extremely confident to purchase this but when used right guarantees victory, when used wrong it is a waste of 1300 gold.


Liandry's Torment:
The burn damage of this is very fun allowing kills that shouldn't have been possible, it also provides some more health allowing you to survive for a slightly longer time.


Hextech Rocketbelt:
This can be occasionally used if you really need more mobility to outplay champions, it is something i rarely buy due to its usefulness being pretty low.


Nashor's Tooth:
This item is fun if you are smurfing that's it.

Katarina's playstyle has always been an aggressive one where you attempt to snowball out of control through lane kills and proper roaming. A lot of the time even when she is getting dominated in lane she can still have a major effect on the game due to her quick and easy botlane roams which commonly result in 2 free kills for your team. You will want to play her around fights around dragon, due to that being when she is most powerful. Once baron fights start to occur her power will be less effective, but if you snowball your lead properly with the Lawnmower Strategy you will easily win the game. The "Lawn Mower" strategy is basically where you and your team get a kill in a lane, take it's outer turret, and then rotate to the other 2 lanes' outer turrets. You then procede to do the same to the Inner Turrets, etc. This is the best way to finish a game where you can't just send all 5 players to steamroll the midlane right through their nexus. Currently she is a pretty strong champion, however with electrocute nerfs, she is disappearing from the meta.

April 22, 2018-Created with a Introduction,Pros/Cons, Summoner Spells, Runes, and began work on Item Section
April 23, 2018-Added explanations for all summoner spells, added images to all sections, and added more runes.
July 9, 2018- Updated it for Patch 8.13 added Playstyle section and updated Items and Runes