Blogs
Five Hops This Time: Kassadin Analysis
Kassadin is a melee mage, adept at darting around combat and disrupting and quickly bursting down high-priority targets, while being able to dish out continuous damage in team fights. He has always been, and will always be, one of the strongest countermages.
His maneuvrability, strong crowd control and reliable gap closers are an immediate threat to most mages in the mid lane. If that's the case, why is he considered to not be viable?
Abilities
Void Stone: After MR, Kassadin takes 15% less magic damage and turns it into bonus Attack Speed. This bonus stacks indefinitely, but lasts up to 4 seconds. Renewed applications refresh the buff.
Part 1 why Kassadin is an amazing anti-mage. Less magic damage is a strong trait in defeating mages, since less damage usually means you get an upper hand. And the Attack Speed... well, that's kind of a waste. It comes in handy in duels though, especially during the early game.
Null Sphere: Kassadin fires a single target nuke, dealing magic damage and silencing the target for a duration.
Part 2 why Kassadin is an amazing anti-mage. Making sure the enemy can't cast spells for 2,6 seconds is a pretty powerful move, especially if you're assassinating. Additoinally, the damage is high enough so that it may whittle down your enemy during the laning phase, before you shwoop in and kill them.
Nether Blade: Passively, Kassadin regains a small amount of mana on each basic attack, with the amount tripled on basic attacks against champions. Actively, Kassadin deals bonus magic damage on his basic attacks for 5 seconds.
Although the mana regen-passive is pretty neat, the active is actually pretty cleverly made up. If your initial burst combo fails, you'll have something to fall back to. Not to mention that the damage becomes pretty neat if you hit someone once or twice.
Force Pulse: Each time a spell is cast in Kassadin's wide vicinity, he gains a stacking buff which stacks up to 6 times. Upon reaching 6 stacks, Kassadin may activate Force Pulse to deal magic damage in a cone in front of him and slow all affected units.
This ability is pretty much the only reason why Kassadin isn't useless in team fights. On the other hand, during the laning phase, this won't deal as much damage or be up as often as Null Sphere will. Even though the damage figures are exactly the same as Null Sphere's, you won't cast it as often.
Riftwalk: Kassadin teleports to a target nearby location, dealing magic damage. Subsequent casts within 7 seconds of the previous one cost 100 more mana, but stack the base damage up to a 10× cap.
If there is something annoying in the mid lane, it's a reliable gap closer. This is exactly such a thing. Riftwalk immediately enables Kassadin to cast every single other ability, and during later stages of the game, it spells death or certain doom for high-priority squishy targets.
Pre-level 6
Kassadin suffers from some standard problems during the early game. Him being melee puts him at an obvious disadvantage against ranged mages. Additinally, he has a very low mana base. What I mean by it, is that his manapool is pretty low when you put it in comparison to his ability costs. He's got some decent mana control himself, but it becomes a difficult feature to manage because keeping your mana up means you're automatically pushing your lane. Additionally, for most of your damage, you'll either pay a lot of mana, or be dependant of your enemy casting spells, as your spells are either on a long cooldown or high in mana cost.
Lv.6 - Lv.13
This would be the stage where you'd be able to dominate your mid lane enemy due to being able to constantly port in, silence, slow, slap, and shove off before they can react to it. Mana problems? Not with Nether Blade I won't. And the farther the game progresses, the stronger you get. Obviously your lane adversary will get stronger as well, but your burst rotation will get stronger and stronger while the enemy still can't cast any spells. And oh well, if we can't get in range, we'll just poop on our enemies with Null Sphere until we can kill them with Riftwalk into Null Sphere, Force Pulse and Nether Blade, and Ignite if need be.
Post-Lv.13
Good fight. If you're fed in the slightest, keep killing those enemies who keep plucking off your allies. They'll be worth lots of cash, and oh well. If there are none, it's either GG or you'll pick off enemies who are worth just about as much as a creep wave or less. And oh, in team fights, keep in mind that you're a melee mage, meaning you're very squishy and easily killed. Sure your manouvrability will occasionally get you out of a tight spot, but it won't be there all the time. And remember that Force Pulse will be up pretty much all the time it's off cooldown, so make sure you spam it hard to get some team-wide damage through.

Team compositions
Kassadin fits amazingly in two kinds of team compositions. First and foremost, he'll fit in any team composed of tanks, bulky fighters, and other kinds of champions willing and able to soak the damage the enemy team is putting out... while Kassadin is not in the fight. It would sound contradictory to what I said before, about spamming Force Pulse as much as possible during team fights, but Kassadin's first and foremost tag is the one of Assassin, and that is what you are supposed to do: assassinate high priority targets. Loop around and carefully take your time to engage in a fight, because in those 5 seconds of cooldown on Riftwalk, you might die.
Second team comp where Kassadin fits greatly into, is a team where he functions as a direct counterpick to the mid. Champions like Katarina or Karthus are strongly counterpicked by Kassadin, as they have strong ultimates... which are channeled abilities (not to mention they're squishy as hell). A quick silence and the game is off for them. Not to mention having a reliable gapcloser functions well against champions who have problems dealing with quick burst damage - champions like Anivia or Orianna - and are unable to dish out good damage as soon as they're up close with someone. Kassadin's a matter of counterpicking and ganking, collecting gold as soon as possible.
Itemization
There's a few good items on Kassadin which are "essential" to him being able to deal damage. Of course, with the stacking manacost, you'll need something to uphold your manabar as-is, or as close to as-is as possible. Mana Regen and an increase in Mana are points of interest. An example itembuild could be:
Sorcerer's Shoes (Homeguard/Alacrity)
Seraph's Embrace
Rabadon's Deathcap
Lich Bane
Void Staff
Athene's Unholy Grail
What I'll usually do, is start out by getting Boots and 3 Potions to go. First thing I want to buy is a Tear of the Goddess to get that stacking working as soon as possible. A Doran's Ring will help out my damaging needs, as a TotG won't add any damage. After that, I go straight Lich Bane. This because upgrading the Tear into an Archangel's Staff isn't worth the money, and the Lich Bane adds another 0,75AP ratio to ye usual spell rotation or R-Q-E-W-shlap-shlap. Next rush is a Rabadon's Deathcap, because you seriously lack some damage with just a Lich Bane and a TotG. Then last thing I do is get an Archangel's Staff to make up for horrible mana control w/o Blue Buff.
After that, it's basically a matter of assessing the situation. Fed AD Carry? Zhonya's Hourglass. Fed Mage? Abyssal Scepter. Enemies stacking MR? Void Staff. I do recommend buying a Void Staff in any case, because it's just an amazingly strong item, especially with the new penetration changes. Last item I like to take either one of the aforementioned, even though my personal preference goes to the Grail, just because of the amazing mana-regenerative passive.
Another thing to note - thanks for the idea, CasterMaster - is that a Lich Bane is not a good idea against a team with high numbers of CC. Amumu, Riven and Taric? Bad idea to get into melee range. 4 stuns will poop on you, no matter the Mercurial Scimitar, Cleanse, Flash and Banshee's Veils. It's not a good idea at that point. Better invest in a Rod of Ages or an early Abyssal Scepter if you desire it so, or maybe even a Deathfire Grasp for ultimate carry pooping powers. Take a good note of how much CC the enemy team has, and correct your build accordingly.
Consideration
So I'm wondering. Why is Kassadin not considered a viable pick in Ranked play, overshadowed by lesser champions in the assassin-field than himself?
Diana: Diana has a gap closer on a very long cooldown if landed without her Q, which is a medium-range skillshot. As far as CC goes: she has a reel-in slow, but that's it. Her ganks are powerful, but the sad thing is: she has no means of disengaging. If she ults in, she's got to get the kill, or die trying, which is kinda not the idea, considering she's just as powerful a snowball as any other assassin mage. Another downside to Diana is that she's sort of an autopusher with Moonsilver Blade; she can't always afford to push her lane.
Katarina: Kata is the champion to see the most rediculous bloom in playtime I have ever seen. And with good right - even though she's one of those plant-face-on-keyboard champs IMO - Kata is without a doubt one of the strongest assassins in the game, being able to shwoop in, kill, and shwoop out in ganks. Good side to it is, Kassadin is a hard counter to Katarina. You want to channel your broken-damage ult? That's cute. Take this ball. Merit to Kata is that "she brings "incredible cleanup potential", as William "Scarra" Li puts it.
Evelynn: While brand new to the meta - from pretty much the least played champ to the top mid laners - Evelynn has managed to secure herself a pretty nice spot amongst the assassin mage brand. Her stealth, along with % Max HP damage, a repeatable slow with Rylai's Crystal Scepter and a slow-cleanse means she's a pretty dangerous girl across the entire map. Not pinking means you're susceptible to her amazingly strong ganks, which could really change the outcome of a game. Good thing is that she's rediculously squishy. As such, Kassadin makes short work of her, no problem.
Akali: I won't go as far as to say Akali is broken, but she is incredibly strong, in pretty much any lane setup. After Lv.6 that is. She has horrible sustaining power, and she has no means to actually harass someone. Her power kicks in as soon as she gets her Shadow Dance and its counters. At that point, she can really deal some hefty damage with high base numbers and a repeatable combo through Mark of the Assassin and Shadow Dance, which is a relentless combo. However, as with all mages: silences are extremely detrimental to what she does.
Ahri: From being a permaban or pick in Ranked play, she has been overshadowed by many a mage, and even more so in the limited field of the assassin. I believe her drop in play comes from her extreme dependence of hitting Charm at the right time. And even though she has amazing sustain through Essence Theft, she is filled with line skillshots easy to predict and dodge, and has meager AP ratios all across the board. Only merits she gets are 3 decent ranged dashes that deal damage, a ranged taunt, and true damage for pooping on tanks. Good thing the latter is badly ratioed as well.
Fizz: If there's one champion - besides Malzahar for taking his daughter - in the League that Kassadin hates, it's Fizz. Fizz' invulnerability destroys half of Kassadin's damage output, and in the meantime, as soon as a Kassadin engages, Fizz will poop on him relentlessly. Not to mention Fizz ganks are among the top ganks as far as CC and damage go. And even though Fizz' jumpiness costs a lot of mana early-game, a quick Rod of Ages fixes most of those problems. After that, Kassadin players are in for a "treat".
Closing words
I believe Kassadin is one of the strongest mages in the game. Manoeuvrability and high burst damage are very strong traits, as well as a reliable second Flash and a backup plan if your initial burst doesn't work. He's a worthy counterpick to a lot of mages, but lacks the amount of team fight pressure some other mages - Gragas, Katarina, Karthus - do possess. He does, however, possess the power to gank extremely well and extremely fast, even with limited items. Farm is not an issue on Kassadin, as he'll get most of his gold from killing high-priority targets within the blink of an eye, making him a strong pick for Summoners who are either bad at last hitting, or have a knack for assassin-type mages with good kinds of damage. In any case, Kassadin is just as easily counterpicked by one of the strongest mages in the League, whose ganks are equally strong and disruptive, and who bytheby has an easier farming time with less dependance of nearby spell casts.

I got ambushed by Elise in brush. This is how low she got me before the stun wore off.

And then I retaliated. That's the power of Kassadin, even at a disadvantage.
Kassadin's an amazingly fun champion. Sure, enemies will rage on you because "You know how to press R" and "Anyone can play Kass", but that's the mere excuse of those who have failed to see the dangers that the Void brings to this world. Get out there and keep 'em silenced, because
