Basically Cassiopeia is an extremely rare champion to see, but if you learn to play this champion even a little bit, she is just awesome at laning and also in teamfights. Cassiopeia is extremely hard to lane against, becouse if you get hit by the Noxious Blast the Twing Fang can hit you 4-5 times during 3 seconds of poison.
It makes me wonder why there is really no Cassiopeia players, even the champion is just awesome, maybe a little tricky at the start, but great after a short practice. Also the speed boost in Noxious Blast makes you ably to chase someone down, spamming a few Twing Fang at the same.

Personally, I take 9 pieces of Greater Mark of Magic Penetration on any AP carry. Mana regen is always useful, even if you will propably get the Buff of the Ancient Golem in 7-8 minutes of the game. This makes you able to spam Noxious Blast and Twing Fang even harder. Ability power Glyphs and Quintensess are quite stantard, you can decide if you take AP/level or the flat ones by thinking if you have problems at the early or late game, or make a mix of them to mid game.

The original 9-0-21 masteries are good for Cassiopeia. If you feel like taking the Burning Embers over Archaic Knowledge but personally I feel like taking the Magic Penetration so you don't need to get Void Staff so early. It's a personal choise again.

Provides you HP, MP/5 and 10 Ability power, but if you feel like you will get harassed hard or the champion you will likely be laning against has long range harassing abilities (such as Karthus, Orianna, Brand, Gragas etc.) it is justifiable to get

catalyst the protector Try to farm as long as you can get this and the level 1 boots if you didnt start with those. Catalyst gives you great lane sustain and is also useful at the late game when you build it into

This item doesn't need explanation, but you can think about the time to get it. It doesn't make too much difference if you get Rabadons before depending on the laning. You can also get the sorcecer's shoes even before big AP items if you feel like you want to gank or just move faster on you'r lane.

If you make it to very late game (or the enemy AD champions focus you very hard) is a good choise, as it provides AP, armor and the unique active.

Some magic penetration against the enemy's squishys with a and for getting the enemy tanks down.

The reason I dont like to build high manapool or MP/5 items is that you should get the Blue buff from the point it spawns for the second time.

The spell I take on any champion

A good choise for AP carry

Other spells to think about:

A good way to chase someone down or get out of the ganks if you'r flash is down. Still you should be able to manage with the speed boost from .

Starting to be a bit less effecient, but still useful for many purposes.

If you want to gank a lot you can use TP ganks, but it requires you'r team to be avare about you'r plans. Works well in premade teams.

Maxing and twing fang makes you able to burst down single enemy champions in very short time. You should also concider taking atleast 1 point in for the poisoning effect in case you dont hit you'r Noxious Blast. twing fang should be the first spell to be at level 5.

Pro's

- High burst and long harassing abilities

- With a little luck you can stun 3-4 enemy champions in a teamfight

- makes it hard for enemy to chase you

- Players at low elo don't really know what this champion can do


Con's

- Takes a few games to learn the mechanics

- Tricky

- Quite hard to master