Okay, to start of this guide I want to first explain why I am making this guide.
When I was new to LoL (just a few months ago) I constantly came to Mobafire to check out recommended builds for champions I wanted to play, and many of them have helped me out, so I know how important it can be for players to be able to find good guides.

Now that I feel secure in most of the champions I play (and those I don't) I hardly come to check out builds any more, but still use Mobafire to check other stuff, and I realized that one of my main champions didn't have a guide above 90% pop.
To me, this means that there isn't a guide up here that has yet been able to quench the thirst of new (or old) players that want to rip people up whilst playing as a snakewoman.

I've had a lot of success with Cassiopeia, both in ranked 5v5, 3v3 and normal games. She was likely the one that got me up to gold rating in season one.

But, just like anyone else, the things I say (especially runes, masteries and itembuild) will just be hints to make your first game(s) easier while trying to learn the basics of the champion.

This is also the first guide I make so I'll be sure to read and take tips from anyone with experience.

Pros

Amazing Harasser.
Good Farmer.
Strong throughout the game.
Passive that allows spamming a lot of spells in one session with low mana-cost.
Slow debuff and Speed buff that allows for both Chasing and Escaping.
An ultimate that can be completley devastating if placed correctly.
Works well with another champion that uses poison.
Imba "/joke"-animation.

Cons

Can be hard to master.
Ultimate is a little tricky to land.
Her damage requires at least one skillshot to hit.
Only two skins.


You might think that I'm not giving you all the cons, but honestly, I can't think of any.

As you can see above, I chose to go with:

x9
MPen marks are unarguably the best runes for any caster in the game, no more reasoning here.

x9
I like to go with these, many people will say that flat mp5 is more useful, but I disagree. It all comes down to your mana management, and if you can control yourself, and only harrass in bursts of 3-4+ spells you won't have any big problems due to . And after your first (usually one) recall(s) you will be high enough level (level 7) to make the /level surpass the flat ones.

x9
These are the ones I play around with the most. E.g. if I'm up against Annie (or LeBlanc, not very often) I can sometimes chose to go with MR instead of AP to survive bursts.
But when I use AP, I prefer /level instead of flat, because it all comes down to mid-late game.

x1
I like to use one of these, because with 9 and this one, you will end up with 10 MPen. Adding will result in 30 MPen which is what most champions have without any extra MR.
You might say;
"But dude, you have 15% spell penetration from masteries."
My answer to that is, percentage based MPen isn't what many think it is.
First of all, %-based comes into the calculation AFTER your flat Mpen has been scaled of.
Meaning that if a champion has 100 MR, you have 30 MPen (boots + runes) and the 15% from masteries the calculation will be like this:
(100-30)*0.15=10.5
10.5 being the MPen your mastery gave you, and not 15 as you might have thought.
Meaning the less MR the target has, the less this mastery reduces.

x2
Kinda self-explanatory, I start with boots and don't want my healthpool to be too low in the start.

As you can see, I like to synergize my "Q" and "E" while leaving "W" at level one and of course taking ultimate whenever I can. (6/11/16)

The reason I don't just chose one spell to max first is because of the utility both "Q" and "E" offers.
First of all, you need to hit with your "Q" or "W" to even start a successfull harass with "E" . (Try focusing on "Q" because it deals more damage unless people decide to stay inside your "W" )
What "Q" does to help your harass is;
1. Applies poison to reduce the cooldown on "E" to 0.5 seconds.
2. Gives you a speed boost that allows you to chase your opponend and land more "E" .

Also "Q" offers much more farming potential than "E" .

Here are the summoner spells I recommend. (Recommended in order from top to bottom)





Honestly, any other summoner spell is just a no-no for me. I guess some people want to go with , but it's a wasted summoner spell that is only good for early game and it's not needed when you learn to control your mana.

Explanation:
Flash is core for me, it's the best summoner spell in the game right now and you should have it.

Ignite is taken if there is no one else on your team who uses it. In my opinion having only one in your team is the way to go, unless the other team has a strange setup with an extreme amount of healers.
It gives you a little bit of boost in your damage to help with kills, and a healing reduce to counter champions like or other healers.

Exhaust is what I take when the player who goes top in my team really wants to use .
It helps you escape ganks, disable any AD-Carry or Bruiser (anyone who deals physical damage) on the enemy team in teamfights and chase people. In my opinion, it's just a better summoner spell than to have more than one of in your team.

Teleport is a cool summoner spell to have, it may sometimes help you land a nice gank, or help your team defend/push a tower. The downside is that it offers zero utility in teamfights and straight up fights, and I don't really like that.

Ghost is a summoner spell that can help you chase or escape, but due to the built in speed-boost and slow-debuff you already have as Cassiopeia I find this an unnecessary and wasted summoner spell.

Cleanse is kinda cool, and can sometimes help you survive ganks or deal more damage in teamfights, but all in all is quite bad right now and shouldn't be used unless the enemy team has an insane amount of AoE CC or is reworked.

Any other summoner spells are not good for you, don't use them.

Items to go with are very game dependant and as such I'm only going to give explanations on when and why you should get certain items.

Core;

this is what I get ALMOST every game, order from top to bottom.


Sorcerer's Shoes are the best boots for damage output, 'nuff said.


Rylai's gives you a lot of health, AP and an incredible slow for all of your spells (It stacks with "W" , but not fully, if you continue reading my guide and read my explanation on Void Staff and how MPen stacks, well that can be applied here to). Note that "E" counts as an AoE spell for to not make it OP.
"We don't want a 35% slow that can be reapplied indefinitely." -Guinsoo.


RoA is one of my favourite items in this game, it gives you everything you want, health, mana and AP. And a lot of it too.
I usually build a catalyst before due to the incredible lane sustain it gives.


Deathcap is the item that gives you the most AP (damage) in the game. Why not get it?

/
I usually get both of these two items, but I focus on if I have problems with an enemy caster or a lot of magic AoE damage, and first if I'm being focused by a champion that deals Physical Damage.


Banshee's gives you even more health and mana, magic resistance and a nice shield to block an enemy spell from damaging and/or placing it's effect on you.

Zhonya's gives you a huge amount of AP while providing a nice bit of armor and the ability to place yourself into a "stasis" making you invulnerable but unable to do anything for two seconds. (move, cast spells etc..)

Situational;

these item's are good against certain setups/champions.


Merc Treads are by no means a bad choice, they give you extra magic resistance and they also reduce the time on CC effects (stuns, slows, silences etc..) on you by 35%, note that only the time is affected, not the effect itself.
Get these if you are up against a lot of silences ( + for example is annoying to face since they both have AoE silences) or stuns.


Quicksilver (or QSS) is an alternative to , and should be purchased when you are up against really annoying abilites that are often placed on you. A few of those are;
, suppress.
, high damage and if you die while you have it on you, the enemy team will get a ghost of you that gives their team an even bigger advantage and gives the caster some of your stats.
And some other really long stuns.


Void Staff is usually recommended by a lot of people to get, and it has it's reasons, this item wasn't put in the "Core" because I usually tend to focus the players with low magic resistance first, like the enemy AP-carry or their AD-carry.
And it's not like I deal low damage to the others afterwards any way.
But if you find yourself dealing very low damage, and the enemy team has a lot of magic resistance, by all means, get it.

Just remember that it wont penetrate their magic resistance by another 40% but rather by 34%, this is because of and how %-based MPen stack in this game (it applies to slows too!).
Let me explain;
If an enemy has 100 MR after all flat penetration has been applied and you have 15% spell penetration from masteries, it will reduce the enemy's MR down to 85.
If you face the same enemy, but now have a too, it gets a little more complicated.
The easiest way to explain it is that first the 15% from masteries get reduced first, so the enemy is down to 85 MR, then the comes into the calculation and reduces the 85 MR by 40% which gives him 51 MR.
The result is the same for this type of thinking, but it's actually not the way it's calculated.
(Note that when I say reduced, I don't mean that he/she will actually lose any MR, just that for you it will be like he/she had less MR)


WotA is a nice item to get when you;
1. Find yourself taking a lot of stray damage from AoE and such resulting in a slow death. WotA will prevent that from happening due to the Spell Vamp
2. Have another mage in your team that wants to get it, if you and another champion in your team have this item at the same time and are close to eachother, it wont just give you and him 80 AP and 25% spell vamp, it will give you a total of 110 AP and 50% Spell Vamp, and that ain't bad.

There are other situational items, but nothing special for Cassiopeia, you are free to use whatever you want! :)

Finally! Everything I've said in this guide up until now has merley been suggestions you can follow if you felt unsure. (Although I recommend you following some because I can promise you, it works. ;))

Anyway, here is where I'm going to try to make you a better Cassiopeia player!

The laning phase can well be the part that makes or breaks your game, if you get denied a lot of farm/exp or ganked much, you wont be able to do very much in the mid game, and honestly, that is where Cassiopeia shines the most.
On the other hand, if you can get a good amount of last hits, maybe a kill or two on your opposing laner (or even the ganker, a few times when people try to gank me I end up getting a doublekill or a kill and survive because of a good ultimate or really good kiting).

As with any hero, you should try to last hit as much as possible, this is your number one priority.
Your second priority should be trying to deny your enemy as much as possible, there are diffrent ways of doing this;
1. Pushing your lane to the enemy tower and hope that the enemy will miss the last hits because of the tower. (This can be very dangerous if you don't have wards and/or good mapawareness)
An effective way to farm while pushing is to throw out your "W" where the enemy caster minions are going to be positioned, but throw it out so it hits the melee ones to. (It doesn't take too long before you can master this)
When the caster creeps stand still, place a "Q" on them and either start lasthitting the melee ones and place another "Q" on the casters when the cooldown is off, or autoattack every caster minion once or twice so they die.

2. Harassing your opponent, as soon as your enemy walks up to lasthit, try to lead them with a "Q" , this will either make your opponent back away and miss a lasthit, or make him/her poisoned, this is where you need to react.
If you think your "Q" is going to hit, start moving towards your enemy, if it connects, start spamming (and I mean spamming) your "E" while constatly advancing towards your enemy. When he/she starts running away from you, try to hit them with a "W" and another "Q" while constantly hitting them with "E" .
Be wary though, don't overextend, and be aware that your enemy can turn around and attack you too, if you have your ultimate, this is where you use it and go for the kill.
A good harass with cassiopeia at level 4+ can get your enemy from 100% to about 40% and sometimes even lower depending on yourself and the enemy. (Morgana for example is a b*tch to harass and very very hard to kill)

A tip here is to use Smart-Cast, it's almost a necessity on Cassiopeia. (Although I haven't bound any of my normal key's to smartcast, I just hold Shift while casting, it's what I'm used to.

One thing that really wins a lane is to kill an enemy while you have a big minion wave, and then push as fast as you can to his/her tower so it kills your minions before he/she can get back. It will result in you being at least a full level higher than your enemy and he/she will have lost a lot of gold, and that's what I call an advantage.

Mid game will be all about continue to farm, but also push and kill stuff. And most importantly, be there for your team.
If you manage to win one or two 4v4 or even 5v5 (or 3v4-4v3-5v4 etc..) teamfights and get kills/assist for that, and maybe even a baron, the game will be in your advantage, and as Cassiopeia, we love this.
If we get a little bit of advantage, we can start roaming and harassing a lot. With blue buff, some wards and a little help from our teammates, we can control the map completely.
So, roam, kill, push!

Late game is basically the same, as it is for many champions too, keep on getting that farm (sounds boring, I know, but it's rewarding), but the team fights will be a lot more important. Since this is a Cassiopeia guide, and not a basic gameplay guide, I wont go through anything more as it's basically the same for any champion.

Here's the most fun and rewarding part in Cassiopeia's gameplay. :)
First some basics.

1. Don't get caught out of position. EVER
2. Don't be too far away from your team when you think a team fight is comming.
3. Always stay behind your team in the start of a teamfight. Yes, sometimes you need to run around your team to get to where you want to be. More on that later.
4. Don't tunnelvision. It's impossible to land a good ulti if you only focus on one target. More on that later.

That's it for the basics, now for the real deal.

Teamfighting

Okay, so what I said up there is really important, If you can position yourself good (meaning don't be a target that the other team sees and thinks "hey, that's an easy target, lets kill her") and still be able to dish out damage you will be one of the deciding factors in the game.
What to do if someone decides to focus you?
Well first of all, a good support and/or tank should always look out for you and your AD-carry, meaning they should keep them away from you as much as possible.
You also have a good slow and speedboost to use at your disposal. If someone rushes for you, try to kite them away a little (by little I mean just a couple of seconds) while dishing out as much damage as possible, then try to make your way around them somehow, preferably someone in your team will have stunned them already.
At this time, people will probably be tunneling someone else in your team, so you should be able to stand and just deal massive damage for atleast a couple of seconds, and a couple of seconds is all we need to kill someone at this point.
If you didn't already know, the biggest tabu you can commit with Cassiopeia in a team fight is using "E" on a target that isn't already poisoned. It will cripple your damage so much it's actually quite sad (because the cool down will not be 0.5 seconds), so always try to land "Q" or "E" on the target you want to damage.
And that's basically it, you will always have to do diffrently depending on the other team, your team and who they/you are focusing.
Always remember to focus the most dangerous person (damage wise at least) and then go through the list, so to speak, AND NEVER GET CAUGHT OUT OF POSITION. I can't stress that enough.

Ultimate Useage

Well, it's not that hard actually, it just requiers you to focus a lot, and observe. As the tooltip says, if the target is facing you, they will get stunned for two seconds (wuut so imba), if they are not facing you, they will be slowed for 60% (aww dat's no guud).
Meaning a couple of things.
1. Always try to stand in a position, that doesn't put you in danger, but makes you able to hit as many champions as possible.
2. Always be on the lookout for where your enemies are facing, and if they are in range (you will need to learn the range by instict to place perfect ultimates).
3. Remember the priority, a stunned support is not as important as a stunned carry.
My priority list is something like this (depending on who is fed it may vary).
AD-AP-Carry / Bruiser-Disabler / Tank / Support.
Don't get me wrong, supports are not useless in teamfights, but they aren't the prio #1. Although one important thing to note, is that if you can catch and kill.. let's say a , before she uses her ultimate, then it will be a much more valuable target than a support that used all her cool downs.

Basically, think like this, as soon as you see an opportunity to stun 3-4 (excluding their support) champions with your ultimate, do it. And when you do, don't focus your spells (apart from "E" ) on one target any more, try to land your AoE spells on as many as possible, while, of course, hitting your main target with at least one of them for continuous spam (this is prefered all the time, but now you can do it with ease and deal A LOT of damage with it).
But don't wait too long, if the teamfight drags on, and people in your team start to die one after another, just use it on as many as possible (don't be afraid to flash to get as many as possible stunned). It's better to hit the stun on two and slow on three, than just a stun on two. It deals high damage too.

Basically, what a good ultimate will do for you is;
1. Lock down the enemy team completely.
2. Give your team time to focus and position themselves even better.
3. Allow you, and others with potential AoE to devastate the enemy team.
And that folk's is all you will need to win a teamfight, and also that's about as much as I can teach you right now.

This is, as some of you might notice, my first guide ever here on mobafire.com, and first guide for League of Legends ever. So I'm glad to take constructive critisim and any advice from you who are more experienced in this field.

Also, if this guide gets some positive feedback I will come and clean it up, put in more details on specific spell-useage, farming and also add clips and pictures of certain stuff.
And don't be afraid to ask me stuff, I might have forgotten something crucial.
Be sure to comment and vote! :)

Thank you for taking your time, and hope it helps. <3