I will post the build first, will work on the explanation soon. Do try out my build, thanks :)

Driven by an intense killer instinct, Katarina uses her talents as an assassin for the glory of Noxus, and the continued elevation of her family. While her fervor drives her to ever-greater feats, it can sometimes lead her astray.
From childhood, Katarina displayed a natural gift for combat. As the daughter of a prominent Noxian general many paths were open to her, but she rejected them all for the path of the blade. Rigorously trained by the finest assassins in Noxus, her father the best among them, it was not long before Katarina demanded her first assignment. The task they gave her was aggravatingly simple: assassinate a low-ranking Demacian officer. As she set to her work infiltrating the enemy camp, Katarina discovered an opportunity too tantalizing to pass by – the arrival of a Demacian General. Stalking him to his tent, she quietly dispatched his guards and slit his throat. Pleased with her impressive kill, she disappeared into the night. Katarina’s elation faded the next day when her original objective, the Demacian officer, led his forces to ambush unprepared Noxian soldiers. Though the Noxians fought valiantly, they suffered heavy casualties. Furious at her mistake, Katarina set off to complete her original task. Returning to the camp, she spied her now heavily guarded target and realized a stealthy kill was no longer possible. Drawing her blades, Katarina swore the officer would die, no matter the cost. She leapt into battle, unleashing a whirlwind of steel. One by one blades flashed and guards fell, each strike bringing her one step closer to the officer. A final thrown dagger restored her honor. Bloody and bruised, Katarina barely escaped the Demacian forces, and returned to Noxus a changed woman. The scar she earned that night now serves as a constant reminder that she must never let passion interfere with duty.
"Never question my loyalty. You will never know what I endure for it."
―Katarina

Voracity is a passive ability that activates whenever Katarina scores a kill or assist, refreshing her ability cooldowns by 15 seconds.


Katarina throws a dagger that bounces quickly from enemy to enemy, dealing magic damage and marking them. Each subsequent hit deals 10% less damage. Bouncing Blades hits a total of 5 unique targets (4 bounces), each striking the closest next target. Dagger Magic Damage: 60 / 85 / 110 / 135 / 160 (+0.45 per ability power)
Striking a marked target with an ability or basic attack will consume the mark to deal additional magic damage. On-hit Magic Damage: 15 / 30 / 45 / 60 / 75 (+0.15 per ability power)

sinister steel
Katarina whirls her daggers around her, dealing magic damage to all enemies in the area. If she hits an enemy champion, Katarina gains Movement Speed for a short duration.
Magic Damage: 40 / 75 / 110 / 145 / 180 (+0.25 per ability power) (+0.6 per bonus attack damage)
Movement Speed: 15 / 20 / 25 / 30 / 35 %


Katarina instantly moves to her target's location and takes 15% reduced damage from enemies for 1.5 seconds. If the target is an enemy, she deals magic damage. Cooldown: 12 / 10.5 / 9 / 7.5 / 6 seconds
Magic Damage: 60 / 85 / 110 / 135 / 160 (+0.4 per ability power)


Katarina becomes a flurry of blades, channeling for 2 seconds throw up to 30 blades to nearby enemy champions. Katarina throws up to 10 blades at 0.2 second intervals, dealing magic damage and applying Grievous Wounds to the closest 3 enemy champions. Grievous Wounds lasts for 3 seconds and reduces incoming healing by 50%. An enemy champion can be hit by a maximum of 10 daggers over the 2 seconds. Cooldown: 60 / 55 / 50 seconds
Magic Damage Per Dagger: 40 / 50 / 60 (+0.2 per ability power (+0.3 per bonus attack damage))

Maximum Magic Damage to the Same Target: 400 / 500 / 600 (+2.0 per ability power) (+3.0 per bonus attack damage)

The reason i max Q Bouncing Blades instead of W sinister steel first is because u can deal more burst damage for the next attack, and more damage for poking. Take E Shunpo at lvl 2 instead of W so u can escape from early GANKS :)