This guide shows the way I play Cassio. She's a lot of fun to play and if done well, she can be a real monster.

I am no high elo player so please consider that before commenting.

I plan to upgrade this guide frequently and add more sections and maybe some gameplay footage later.

2011-11-17
-Some grammar cleanup
-Changed runes a bit

I go with ability power quints, magic penetration marks, manareg/lvl seals, AP/lvl glyphs

You can choose flat healt seals instead of manareg and replace the AP/lvl glypsh with flat AP for a stronger early game

With the old mastery system, I went with a standard 9/0/21 caster build, but with the new masteries I changed to a more offensive 21/0/9. It worked out really well, I usually don't have mana problems in early-mid game. Blue golem helps a lot.

The 9/0/21 build can be viable these days, but a haven't played it too much so I can't say anything specifical about it.

For Cassiopeia, Flash is a must I think (even after the nerf).
For the second slot I usually get Ignite, it helps you secure kills early game, and halves the lifesteal and regen of champions like Mundo or Swain, . In some situations (a lot of ignite in team) Clarity can be a viable choice as well, with it you can spam your Q all the early game, sending back champions to base -> less minion kills for them.

- Has extremely low cooldowns on Q and E(if poisoned)
- Early game harassment is one of the best.
- Great duelist
- Really good farm


- Squishy early game
- Ultimate is highly situational, and needs Cassi to move closer
- Usually gets focused

I get Doran's Ring first, it has a nice amount of HP and manareg which helps a lot in the first few levels. I hardly ever get a second ring because usually I get to harass better. After that I rush for Sorcerer's Shoes for obvious reasons.

One of Cassi's core items is Rylai's Crystal Scepter it has HP for survival, AP for more damage and a fantastic passive, with it you will be able to kite way more effectively.

Then I get Rabadon's Deathcap to get a large portion of my AP so I can do some real damage.

I add Will of the Ancients and Rod of Ages for additional survivability and damage.

After I sell Doran's Ring I usually get Void Staff to deal more damage to enemy tanks and offtanks as well, if the enemy team has no real magic resist take some armor( Zhonya's Hourglass) or MR( Abyssal Mask) depending on the enemy team.

Deadly Cadence (passive)

After casting a spell any subsequent spellcasts will cost 10% less for 5 seconds. This ability stacks up to 5 times.

This passive is one of the good ones, you will be spamming spells a lot so it will save a lot of mana for you

Noxiuous Blast

Cassiopeia blasts an area with a delayed high damaging poison, dealing 75/115/155/195/235 (+0.9) magic damage over 3 seconds and granting her 15/17.5/20/22.5/25% Movement Speed for 3 seconds if she hits a champion.

Cost 35/45/55/65/75 Mana
Range 850

The skill why I love Cassiopeia. Has a 0.9 AP ratio, a great range and its AoE so it is fantastic whet it comes to farming. I max this first, because of the larger range and farming capability. Use it for heavy harassment early game. If the enemy thinks he/she can shrug of your poison and closes in, start spamming your E to make them reconsider.

Miasma

Cassiopeia releases a cloud of poison, lightly damaging and slowing any enemy that happens to pass through it.
Cassiopeia releases a growing cloud of poison that lasts for 7 seconds. Any enemy that passes through it is poisoned for 2 seconds, dealing 25/35/45/55/65 (+0.15) magic damage each second and slowing them by 15/20/25/30/35%. Continual exposure renews this poison.

Cost 70/80/90/100/110 Mana
Range 850

A larger area of effect poison, which expands over time, does decent damage and it slows. I use it mainly to keep the target(s) poisoned in case I miss with Noxious Blast. I max this last because rank 1 is enough for farming with Noxiuous Blast and it keeps the enemy poisoned just as rank 5 would.

Twin Fang

Cassiopeia deals 60/95/130/165/200 (+0.55) magic damage to her target. If the target is poisoned then Twin Fang's cooldown is reduced to 0.5/0.5/0.5/0.5/0.5 seconds.

Cost 50/60/70/80/90 Mana
Range 700

A skill with 0.5 sec CD without cooldown reduction ? Yes this is that skill just keep the target poisoned and you will rape them. It has a 0.55 AP ratio, but it still has a 0.5 sec CD if the target is poisoned, amazing skill. I max this second after Noxious Blast for greater single target damage.

Petrifying Gaze

Cassiopeia deals 200/325/450 (+0.6) magic damage to all enemies in front of her. Enemies facing her are stunned for 2 seconds while enemies facing away are slowed by 60%.

Cost 120/160/200 Mana
Range 750

Cassi's ultimate, just a look i nto your eyes and BAMM a long stun and damage. It is not bad in 1v1 situations, but it shines in teamfights where you can stun 2-3-4-(5) enemies at once for 2 seconds, it can turn the tides of a teamfight. I put a point on it whenever it's possible.

Cassiopeia is the best when played in the mid lane as an AP carry. Her early game is insane she can harass the hell out of enemy casters.

While at level 1-3 don't bother using your skills to farm, just harass the enemy champion and use your autoattacks to lasthit minions.

At level 4-5 you can start to harass more agressively (if you havent done it before) so when you hit level 6 the enemy mid laner is lower on health so you can kill him with an RQWEEEQ combo easyly if you manage to stun him/her.

If the enemy mid laner is hugging tower you can consider ganking bot or top (ask if they set wards or not) Start with a QW combo and close in for a flurry of Twin Fangs.

Some easy prey for Cassi: Veigar Ryze

In general, cassi is strong against champs that dont a fast gap closer or have a smaller range than you.

Some counters to her: Katarina Kassadin

Cassiopeias greatest weaknesses are champs that can dodge your Q teleport in your face and kill you in an instant. (Kass even has a silence on top of his ult)

Throw Noxious Blast and Miasma at the caster minions, and then focus on the melee minions whith your aouto attacks or harass the enemy champion.

I havent tried jungling with her yet, but I hear it is viable, and has extremely strong lvl 2 ganks. Start with golems, get level 2 get a point on twin fang, and gank bot lane. They will be surprised.

If your jungler can bear the loss of blue buff, ask him/her to let you take it, it will help your early-mid game a lot.

That's it for this guide, feel free to comment, write what you like/don't like about this guide and I take good advice with Cassi as well.