I know what you're thinking. This build is just a troll, and to some extent you might be right. However, I have brought this build into ranked play, and whilst only having tested the build low elo (mid Gold), I think this build has potential. Here's Why:

Zz'Rot in many ways counters Katarina's biggest weakness; punishment from roaming, and low hp regen. Essentially the premise of this build, is that you aim to go even pre-Zz'rot Portal, place it down mid and begin to roam. If the enemy mid laner follows you, you begin to accumulate tower pressure, so even if you go even in your gank, you are slowly winning Mid. If they stay Mid, your Zz'Rot minions will help defend your lane, and you should get at least one kill, especially bot lane as you will be level 6 by the time you complete your Zz'Rot.

Pros;

• Tanky; the 55 Armour and Magic Resist will help you survive not only in lane, but in your ganks, which with some follow up damage should result in you getting kills and beginning the snowballing.
  
• Cs'ing: I don't know if it's just me but I don't find early game Katarina to be very easy to CS with. However since building the item, I have found myself going either even with, or beating my enemy laner in Creep Score, increasing your gold income and hence again your snowball potential.
  
• Health Regen; one of Katarina's biggest weaknesses is her low base health regen, meaning you can easily get harrassed out of lane by any smart player. The bonus health regen (125%) helps you enormously, increasing your pushing effect by allowing you to stay in the lane longer.

Cons:

Damage; you are obviously sacrificing rushing damage for the sake of this item, which I believe to be worth it as with just one succesful roam, you will start snowballing into your Luden's Rush, and should still stay ahead.

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