When reading this guide and you find don't like it, give me some constructive critisism. If it didn't work for you in game, tell me why it's flawed; Or if my structuring of the guide is bad since this is going to be my first one.

There have been some great guides of Kassadin on this site, they really got me into using Kassadin. But I adapted him to a different playing style just slightly because Kassadin isn't too much of a versatile champion such as who can play as a tank, AP and/or jungler.

Kassadin is a very slippery champion and very capable to dealing massive damage to opponents. Utilizing all his abilites and planning ahead will lead you to a successful game.

Pros:
- One of the best nukers
- Able to escape/chase well
- Silence + Slow
- Squishies fall to Kassadin
- Good 1v1 champion

Cons:
- Not too strong early game
- Primary target in team fights
- Squishy, if a problem buy health + AP substitutes
- Making poor decisions will lead to easy death
- Prone to CC (Crowd Control)

Most of the runes I use cover the essentials for a caster.

Common for Kassadin users for the extra Magic Pen. to go along with the .
Greater Seal of Replenishment and Greater Quintessence of Replenishment are both for Mana Regen. because Kassadin can harass well starting at level 3 or 4.
gives Kassadin more nuking force.

These aren't in any specific order, but there are a few that I feel make better starting items than others.

Main Items:

I usually start out with this item because it helps to start using it's Passive effect early for better late game.

Most caster/nukers get this item for the serious AP boost it gives. I usually get it later after all the items that make Kassadin survivable. It's better to stack mana early game to stay in lanes longer. But this item helps when kills are a factor late game.

Buy this item if your doing very well early game, right after or .

Important for Kassadin because he is very vulnerable to CC. This is another prevention along with Cleanse. is an alternative to this, but Banshee's Veil gives nice Health (works when MR > Health is needed).

Main shoes for caster. Works in sync with . If enemies do not pick up Magic resist at all, Ionian Boots of Lucidity can be a good choice as well.

At this point, the game is usually done and I don't need any of these items, but if it does last long enough, this is a great item to get. Kass usually has a few seconds of all spells being of cooldown. This would buffer the time without abilities available. Also gives him a small movement speed boost.

OPTIONAL/6th SLOT ITEMS
AP, Mana Regen and Cooldown Reduction? Very nice for nukers like Kassadin.

Good for when there isn't much CC at all of the other team or when your team has an extreme lead in the game. But overall would be the best item to build.

Alternative to if there is a lot of DPS on the other team OR they have a champions such as or or to counter their ultimates.

Kassadin lacks health and an item like this would make you more durable in team fights or 1v1s in general.

Kassadin's silence and really his biggest source of nuking. Works very well against squishies. Isn't much of a force early game but it scales really well into late game.

A small boost to Kassadin's play, just pop it in when you need to stack for Force Pulse and [Archangel's Staff] or heading in to a fight. Remember that it also gives the passive ability to gain mana per melee attack. This ability takes almost no mana to use so active it whenever you can. This ability helps with last hitting minions.

AoE slow and Damage. Just like Null Sphere, it gives a ton of damage, but the downside is that it needs 6 charges to become avaliable. AS mentioned in above, Nether Blade can charge it up quicker.

Many Kassadin players' favorite ability. It lets to teleport around like Ezreal, with a moderate nuke whereever you land. The more "charges" are on it, the more damage it will do. Very mana consuming. It becomes deadly with enough AP late game. This spell lets you turret drive in and then teleport out. Also, it makes you more mobile and quicker getting somewhere by taking shourtcuts through the wall. Using this in team fights help position your self into a better spot to Q and E ot using it to escape/chase/kite.
Not too noticable during the game, but can help without you even knowing it, gives a nice MR and converts that into Attack Speed.

Start the game off with Null Sphere as it is your biggest nuking ability you have. Then to Force Pulse, your secondary damage ability. Repeat Null Sphere and Force Pulse until you get to your ultimate, Riftwalk which if your in and out on fights or just mobility purposes. Once you hit level 8, learn a Nether Blade to help you stack up Force Pulse charges. And after that level up Null Sphere whenever you can, then your ultimate whenever you can, finish up Force Pulse and finally get the last 4 levels of Nether Blade.

Cleanse is taken by many Kassadin players and really benefits him in all types of situations invoving CC or heavy spell damage. If your building a Banshee's Veil, you will then have at least two CC buffers.
I prefer this spell over others because early game the damage output just isn't enough to finish the enemy without them escaping. Use this again healers such as Soraka, Dr. Mundo, Taric so their healing gets a major reduction.
Good for if you are going to use A LOT of mana and constantly spam spells. Why I buy Archangel's Staff instead is that I get more out of the item than a spell that has 1 purpose.
Flash is one of those spells that summoners like to take on Kassadin to make in a more potent in and out champion, better chaser/escapee. I rarely use flash only because of the short cooldown on his ultimate already.
Gets you back in the lanes early game or team fights late game. Kassadin isn't a backdooring turrets champion, but a good pusher. When you get most of your item build, you can pretty much one-hit all the minions in a wave with Force Pulse. If there is a ward/shroom/jack-in-the-box you c an teleport onto, you can catch a stray enemy by surprise.
Not too important because you will be nuking them in seconds, but if you see lots of DPS on the other team in champion select, get this in replace of another spell.
Helps with chasing and global map awareness, but it's hardly used usefully. Unless you have a good hunch for where theye are or your just lucky, it usually doesn't help too much.
Wouldn't recommend this, but helps in a moderate way. Chasing and Escaping already is already a piece of cake to Kassadin. Ghost is useful on Kassadin in Dominion.

These spells are here for some obvious reasons. Heal can be useful, but shouldn't have to be used with Kassadin's maneuverability. Fortify should be taken by another champion besides Kassadin, usually the tank or support who do not need luxurious summoner spells. Revive is taken by champions who have global abilities which Kassadin doesn't have and is hard to fit into a play style.

Early Game:

Start out with Sapphire Crystal. If you're laning last hitting helps get you your gold needed for your build and gets your opponenets pushing you to your tower which will help when you and your partner get to level 6 because when your opponents think that they get too over confident, coordinate with your partner (and/or jungler) for an attack. Kassadin is amazing when it comes to ganking. Teleport in with Riftwalk, silence/nuke with Null Sphere and slow with Force Pulse. Remember to line up that Force Pulse on maximum number of champions. If they are running away, Riftwalk in front of them to cut there path off, they will either keep running that way to their turret or that a detour. Watch out of players who take flash! When you find time, remember to gank. Kassadin can take many players by surprise by teleporting in without time for the target(s) to react. If they use summoner spells like exhaust, use cleanse to take it off (if you brought it). Remember that cleanse can't take off ignite. When If you are successful early game, you should start to build Mejai's Soulstealer.

Mid Game:

If your early game wasn't up to par, start thinking about alternitive items to build that would counter your difficulties against the other team. Mid game usually is the time where ganks start to occur, so be on the look out and listen to those MIAs. Major CC teams can take down Kassadin if not careful. Stay close enough to your team that if your in trouble they can rush in to help you or vice verse. By now you should have an Archangel's Staff, Banshee's Veil and Sorcerer's Boots.

Late Game:

You should be level 18 or so by now and so should everyone else. You should do some final farming to finish your build if you haven't yet. If your out of mana, hit enemy minions because with Nether Blade, you can regain 20 mana per pyshical attack. At this point it all comes down to team coordination, if you don't work with your team, you will die too soon and give your team a 4v5 situation. As a mage, stay behind your teammates, perferably the ones with a decent amount of health. As this point it's not about getting all the kills, unless you still have stacks to go on Mejai's Soulstealer. Though you can do a lot of damage, don't get too cocky and turret dive under a disadvantage.

Kassadin works very well with caster that have short cooldowns, cause they have with charging his Force Pulse (Works against enemy casters too).

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Good allies also make good enemies. Force Pulse still gets charged when an enemy uses a spell. Karthus seems to be to best with his Lay Waste but Kassadin still can benefit from most champions. Also, squishies are an easy target for Kassadin. A Null Sphere can be deadly at level 3 to them.

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There are the champions that might give you a hard time. Some of these might be tanks that stack up a lot of MR (Magic Resistance). If this happens, either buy Magic Pen. or attack them as a team but don't focus them first. Other nukers may be a problem too with their crazy damage output like you. Champions with CC can hurt as well too if you didn't bring Cleanse. Sometimes DPS champions will hurt, especially the ones that have speed and flashing abilities, but Riftwalk can always save the day.

Kassadin is one of those champions that is unstoppable if fed early on. He has a very noticable nuke even with no AP items at level 3 to most champions which makes many players afraid of him. Play wisely and you will win almost every game (or at least do very well yourself). If you read all the way to here, thanks for reading. Again, if you have any constructive comments, plesae post them.