Heeeeeeeeeeeeello there, this is my first ever guide on MobaFIRE and my first guide in general. My mother language is french so I might do some typos/grammatical mistakes. Plz don't complain. Oh and I'm only level 27 so I don't know alot of things. PLEASE leave some POSITIVE feedbacks! Enjoy x)

My choice of runes is pretty simple and goes well with the role and how I play Kassadin.

Greater Mark of Magic Penetration
As explained in this guide, these runes procure more damage than the Greater Mark of Ability Power. That is the main reason why I chose these. They give an additional bonus of Magic Penetration with the Sorcerer's Boots you will build later in the game.

Greater Seal of Mana Regen
Kassadin's ultimate and other skills require ALOT of mana (Reason why I build Tear of the Goddess). These runes are VERY helpful when you don't have blue buff (It can be because your jungler needs it or the other team stole it)

Greater Glyph of Ability Power
This is your main choice of rune for damage. These runes are almost ALWAYS used by AP champions. I don't think I need to explain more in details.

Greater Quintessence of Ability Power
Same scenario for the Quintessence. They bring ALOT of damage, most than any Quintessence. Simple choice right there.

In this chapter, I will try my best to explain all the items I chose and the order I think is the more efficient. Enjoy :)

When you spawn
You should always buy a Cristalline Flask (The best item for sustain IMO) + 3 Health Potions/2 Mana Potions for additionnal sustain. In addition, a ward is essential and you should ALWAYS have a ward in your inventory. Wards prevent you from getting killed when you are < level 6.

Sorcerer's Shoes
These boots gives you a great amount of Magic Penetration in addition of your Greater Mark of Magic Penetration. You can either buy these boots or the Ionian's Boots of Lucidity (CDR).

Rod Of Ages
A good item to get early so you can exploit the full potential of this item. It makes you tankier and gives you more sustain in lane and in general. Since Kassadin is a pretty squishy champion, this item is primordial.

Lich Bane
Extra Mana, extra Movement Speed, extra AP. This item is extremely powerful when used with Nether Blade... your basic attacks beome extremelly powerfull. A GREAT item for Kassadin.

Rabadon's Deathcap
The ULTIMATE item of Ability Power on EVERY AP Champions. It is simply one of the best items or an AP Champion to buy. Essential to do ALOT of damage. I don't think I need to explain alot because this item is the most used by AP champions.

Zhonya's Hourglass
A perfect item to be a little tankier and be less vulnerable when Riftwalk is down. Thanks to LiLStormcloaK for pointing that out :)

Farming is ESSENTIAL for Kassadin. In the early levels, it will be pretty hard to farm, but when you will reach 6/when you will max your E, the farming is gonna be easier. Without alot of farming, Kassadin is weak. He is dependant of it.

Riftwalk (Max 1st)
This skill is the same as Flash but you can use it every 6 seconds + it does a significant amount of damage. GREAT for farming, ganking and getting out of rough situations.

Null Sphere (Max 2nd)
This is gonna be your main damage/harrassing skill early game. It is a VERY usefull skill because it silents the enemy PLUS it deals a great amount of damage. When you play versus AP Champions like Katarina or Anivia, a skill that can silent is very efficient.

Force Pulse (Max 3rd)
This skill is extremely usefull in teamfights. Why? Lets take a look at the description of this skill : ''Kassadin draws energy from spells cast in his vicinity, gaining a charge whenever a spell is cast near him. Upon reaching 6 charges, Kassadin can use Force Pulse '' In teamfights, everyone ususally spam their abilities so you EASILY reach charges. We max this skill in third place because teamfights at level 1-8 aren't really frequent + your Null Sphere is a great skill to harrass the enemy.

Nether Blade (Max 4th)
This skill is great for last-hitting minions, excellent when you have a Lich Bane and for basic attacks in general. Although this skill is usefull, I find the others more important to max first.

I hope you guys liked my guide and remember guys... this is my first Guide EVER + I don't know much about the game (I'm only level 27 in LoL). Please take that in consideration and leave me some FEEDBACKS in the comment section!

Thanks for reading :D