Welcome to the unconventional, but amazing Kassadin guide. While many people see AD Kassadin as a pure trolling build, he is a beast when in the right hands. Unlike AP Kassadin, you don't die directly, and your damage output is much more consistent.
I'll cover the details in this build, and please message me if you find any bad spelling or other details.

This build will be updated as i get more time.

Hi everybody, I'm Masqerade, long time AP Kassadin player and although not the best, undisputible not the worst. I grew tired of being so snowball dependant. I mean, if Kassadin gets a bad early, he's worth nothing. AD Kassadin on the other hand will be a great asset even if your early game is a little bit shaky, and can recover much easier.

The runes i use for AD Kassadin is my normal Off-tank setup, which looks like this.

For marks i go 6 Greater mark of desolation and 3 Greater marks of strength. I find that this, in combination with my quintessences give me a really good capability to last hit, and also makes me dish out good damage in early fights.

For seals i go with 9 Greater seals of resilience. This gives me a hefty 13 armor, which makes up for being melee by letting me ignore harass like nothing happen'd.

For glyphs i go 9 Greater glyphs of warding, making me more totally immortal to early magic damage in combination with my passive.

For quintessences i go 3 Greater quintessences of strength. These babies is what makes farming childs play.

If you wan't to, the seals can be switched for mana regen / per lvl and glyphs for magic resistance / per lvl. This is more important if you go mid as usual AP Kassadin does, as you need more mana for harassment and your magic resistance will be more important.

My masteries are aimed at making me tough enough to stay in lane, but still give me that little extra armor penetration to not fall behind in damage.

They can be changed for a 21-9-0 or 21-0-9 if you wan't more damage output, but i find this one more reliant and safe.

For starters you go with a Dorans shield. This means you will have about 40 armor and some extra hp regen. Get starting Boots and rush Sheen. Upgrade your Boots to Mercury and grab Emblem of valour if you can. Get Recurve bow and upgrade into Stark's fervor. Rush Zeal then finish your Trinity force. After this get a Guardians angel for some defence and security.
I then go a Bloodthirster and Infinity edge, starting with Bloodthirster if more lifesteal is your priority and Infinity edge if your damage ain't all you wan't right now. If you feel that survivability is more of a problem than damage, get a Banshes veil or Warmogs armor.

I usually go with flash and exhaust, but i will go through the ones i use.

Main choices

Flash

Flash is mostly there for the pre-6 gank safety, and is not an option carved in stone.

Exhaust

This is the ****, and the only one i always use. No matter if it's to save your life, ensure a kill or win the teamfight, Exhaust is always there and a gamechanging summoner spell.

Teleport

If you feel sure about the pre-6 laning you can grab Teleport instead. This let's you farm more effectively and recall without being afraid of getting behind in experience and gold.

AD Kassadin is a distinctive character thanks to his massive damage output combined with both giant amounts of mobility and quite some CC. But you gotta understand that at the same time he got weaknesses which can be exploited.

Pros

- Mobility. This is the keywork in any Kassadin build, and this one ain't different.
- Consistent damage. Your damage output is strong and steady, but at the same time your Trinity force will provide that little burst when needed.
- Tankiness. While most people won't notice it when looking at the items at first, AD Kassadin can absorb more damage than most other with this much damage. Your passive renders mages, the main assassin counter, useless and your guardians will deny most kills from AD carrys and Off-tanks.