Greetings! I take it you want to enjoy the benefits of being an absolute bad-*** in dominion? Then Kassadin is the champion for you. I played him quite a bit in dominion and I found this build to be very interesting to play. You might have noticed this build is a little unorthodox. Not ammasing AP on Kass? Wtf? But trust me on this.

This is my first guide on MOBAfire so please bear with me, and understand that by no means I claim this guide to be perfect. This guide works for me because it has great synergy with my play style, but it might not for you. So we understand eachother? Good. Read on.

Pros:

Great Damage
Great Survivablity
Great Ninja capper
Awesome looks and voice

Cons:

This build relies on the majority of your enemies being AD carries, too much enemy mages can shut you down pretty hard
Build used 3 item actives, can get confusing
Build sacrifices early game damage for survivablity

I pick fairly standard caster runes, but you can have a lot of variety in them.

Greater Mark of Magic Penetration [flat Magic Pen]
You want this, these are the only runes you absolutely MUST get. No magic penetration equals one sad Kassadin that is eaten alive.
Greater Seal of Scaling Mana Regeneration[mana regen/level]
I pick these so I will have less mana issues mid/late game, to compensate for the fact that I don't buy any mana items. You can go for flat mana regen, or even mana if you want the benefit of spamming your spells early game, but be prepared to run out mana late game.
Greater Glyph of Scaling Ability Power[AP/level]
The Glyphs are optional. I like these so I scale into mid/late a bit better but a lot of people prefer cooldown glyphs on Kassadin. Play around with these to find what suits you better.
Greater Quintessence of Ability Power[flat AP]
Again, these are optional. I like to get these because I don't buy AP early on but you can replace them with just about anything magic related. Flat health also works wonders on your survivability. Also play around with these to find what works best for you

Masteries, well well well. Not too much to say here. You COULD go for 9/0/21 and have more mana but this build focusses on surviving. What use is more mana when your dead before you could spend it all? The offensive tree is pretty much set in stone for AP casters. I like to take 21 points in defense to make Kassadin very, very, VERY hard to kill. Also improved cleanse will save your ***.

I like to take Ghost in dominion on pretty much every champion. Dominion is all about movement, and ghost allows you to get to the Windmill faster at level 3, and it can make the difference between losing a point and cleaning up a silly Shaco trying to ninja cap you.

Cleanse is just my personal preference. It turns you from a Kassadin that is extremely hard to kill into a Kassadin that is near impossible to kill. And I just like the look on people's faces when they can't kill me. :)

Alternatives, based on your preferred playstyle:

If you just can't stand running out of mana. I still advise against this spell due to it's long cooldown, and if your riftwalking you will deplete the mana you just gained in 1 cast anyway. It might secure you a kill, but smart use of your skills can do that too.

For the people that want to have the extra bit of damage, and want to shut down a Jax with 5000% lifesteal.

For the people that don't think buying a hefty bunch of armour isn't enough to troll AD carries. And for those who want to slow people that they missed with their E.

For the people that don't want to walk. You really, really don't need this spell. But if you the type of person that wants to fly across the map in zero seconds flat, by all means take Flash.

Anything else... I would advise against. If you like pushing creeps bot, maybe take Promote, if you get killed by turrets all the time, by all means take Garrison. But this build isn't for Kassadin pushing creeps, and Kassadin is one of the best turret divers in the game, so your probably not using your spells right if this keeps happening.

Maximize damage early on. You can grab a point in W at level 3 if you want to charge you E yourself, but I suggest you don't grab your W at all until you maxed both your Q and your E. Now to the fun stuff.

Your combo should consist of QERQR (repeat QR until target is dead). Use Riftwalk to get into range when you have to, don't forget that tagging an opponent with your slow (E) can secure the kill for your team even if they still have a lot of health.
In large teamfights try to hit as many people as possible with your E and try to watch for targets you should silence. Channelled abilities such as Malzahar's Nether Grasp can be interrupted by you. Other targets you should watch out for are Nunu's Absolute Zero, Miss Fortune's Bullet Time and Katarina's Death Lotus. Interrupting an ultimate like that can mean the difference between them acing you and you acing them.
One of your biggest roles is to chase survivors in the aftermath. Your a great chaser capable of hopping over most barriers in the map, use this to your advantage.

Aahhh, Items. This is where this build shines. Let me talk about the core build first.

CORE:


This item makes this build stand out. Because of this item, you can laugh those AD carries in the face as they pound away at you and you just don't die. This items allows you to be screwed over by your cooldowns and get 2 seconds of troll time to wait for them. This item, period.

This item allows you to ninja so easy. It also allows you to stay in the game much, MUCH longer without recalling. You can kill an enemy to take his point, and by the time he comes back to fight again you are full health again. Also for those 'I need to be faster RIGHT NOW' moments.

The item, the AP, the legend. Without this item your lategame will be very bad, you may not die, but you wont kill either. The 100 AP from Zhonya's only take you so far.

More magic pen? Also a nice AP boost? Yes please. Unless your the only mage on your team (and even then) the enemy should have figured you mean trouble by now, and bought some MR. Buy this to continue laughing at them.

Spell Vamp, Lifesteal, Damage, AP, an Nuke. Give you more survivability, and makes your auto attacks actually do some damage (though not much, don't rely on them)

ALTERNATIVES:
Abyssal Mask 3/5 or more enemies are high damage mages? Buy this right before Hourglass.

Rod of Ages Still getting your *** kicked out there? Running out of mana? Get this. (early in the game, but after Hourglass)

Archangel's Staff Running out of mana too fast? Not enough AP for your liking? This is the item for you. Get it just before or instead of a Deathcap.

Lich Bane You don't want to be completely useless when your spells are on cooldown? Get this item instead on gunblade, and earlier in the game.

Rylai's Crystal Scepter If you want to slow and be even harder to kill.

19-10-2011: Initial Release.

I will add more Dominion specific information soon and more strategy. Enjoy!