Hi everyone, I did this section in order to explain some few things, and ask for some help.

This build is under construction and I'll try to complete it as fast as possible. Even if it's not finished, i would appreciate some comments, and feedbacks, if you have tried it, or simply what you think.

You will also notice that I'm not engligsh, and I will appreciate some help with the language. I try to write something easy to ready, with somes "jokes". So some grammar mistakes would be annoying.

There is a lot of strange things in my Build.
About Runes / Masteries , goals etc.

CDR Runes

I love CDR, because it allows you to use your spells more often. And Katarina is totally spell reliant. So In my opinion, 10% CDR free at Lv 1 will always be Good. I will almost ALWAYS take that over MR. Because it will allow to take more creeps with Bouncing Blade, survive with Shunpo. I will still consider some MR against some LeBlanc or Heavy burster.

AD Runes

Sadly almost EVERYBODY wont understand that Katarina scales with AD. These runes add 82.5 damages to Death Lotus at Lv 18 + damages on auto-hits.

Swaping Boots in the very late game for Lucidity is very important, due to the CDR which is Vital late game, because you will need to avoid as much as possible damages, by using Shunpo in order to deceive your opponents, and in order to use Death Lotus Twice in a teamfight.
I will also sometime pick Lucidity early when the opponent builds no MR and they mostly have carries.

Early Alacrity

I Pick Alacrity very early, often after Zhonya's Hourglass, because I want to ALWAYS catch my targets and I would appreciate to escape tight situations, with my extra movment speed boost + Sinister steel buff.

Mostly Resistances in the Build

I build lots of defensive items, which give damages to my spells. Why ? . . . Well First of all, Katarina naturally has tons of damages. And he doesn't need to be full Ap Builded in order to kill Carries. Katarina also benefits more of Magic Pen than Flat Ap. This is why Haunting guise and Abyssal scepter are my favorite ones. You will also need to stay alive, in order to not feed, and to keep the fight up.
An other reason is that you will stay low ealthed Longer. Then Malmortius Ad bonus will be even more reliant. And a weel casted shield will keep you close to death, but will also del the Maximum of damages.
So you probably understood that Malmortius is the MAIN item of the build. ( Death Lotus Benefits more from AD than AP )
You will also need a Guardian angel, because you will play with Death, in order to do your job.

Shield

It's really easy to understand that. ( I guess )
You don't need Ignite. You will not target tank anyways, and you have enough damages to take Carries down ANYWAY . But it may help you to Snowball easier early.
Barrier will grant you a huge shield, which will protect you during your Death Lotus it will also save your life early. Kata is seriously easy to kill early, and a Barrier will often avoid a death.

Skill Order FTW ?

Bouncing Blade is an important spell for lane presence. It allows you to harass, farm, and to damage the opponent. Upgrading it will also reduce CD. Best damages upgrade of the 3.

Shunpo is your movment spell. You WANT to stay alive, so you will need to lower the CD by upgrading it. Even it gives less damages than Sinister Steel. It will also allow you to use it twice on the same target. Or to chase.

Sinister Steel. I mostly consider it as a Tool in order to complete her kit. Not as an important spell.

What You will Expect

What She will Expect