Cassiopeia, while unimpressive at first glance, blossoms into a brilliant DPS/spiker late-game. She has an amazing AoE crowd control that is useful for chasing, running, or even initiating - she has an extremely spammable damage spike skill, and she works best in a team with Teemo or Singed to fully exploit her poisoning abilities. This build focuses on giving Cassiopeia a set role as the mid carry, using her excellent harass early game, transitioning into a deadly ganker mid-game and a team DPS support late-game.


Pros:
-Excellent minion farming abilities with Noxious Blast
-Great champion harasser with both Noxious Blast and Twin Fang combos
-Amazing solo chaser with the increased movement speed from her Q and the snare provided by her Miasma
-Fantastic AoE ultimate in Petrifying Gaze
-Strong staying power with mana regen runes and items, combined with her passive.
-Extremely strong in conjunction with Teemo or Singed

Cons:
-Squishy caster with a very small amount of burst damage
-Deals negligible damage if unable to land poison on the enemy
-No reliable escape mechanism - although your W and ultimate do CC
-Relies heavily on spamming her E, meaning that she is very vulnerable to silences



Deadly Cadence - Her passive. Every time she casts a spell, her following spells cost 10% less. Stacks up to 5 times. This is very useful as it means you can spam Twin Fang with almost no worries of running out of mana. This also reduces the cost of your Ultimate when you do decide to pop it.

Noxious Blast - Her Q, and very similar to Karthus's Lay Waste. Use this to farm minions as well as harassing, but most importantly, use it to poison your enemies to mark them for Twin Fang. Max this skill last - the poison is what is important.

Miasma - Her W. Essentially you create an area that becomes poisoned for the next few seconds, and enemies inside the zone will be poisoned, will take damage, and will be slowed. Since the range is wider than your Q and it is instant, this is a much more reliable spell for poisoning enemies. This is why you max it second. It is very useful as an escape tool as well as a snare for chasing enemies.

Twin Fang - Her E, and your bread and butter skill. Twin Fang deals decent damage on hit, and recharges almost instantly if it hits a poisoned enemy. This allows for extremely effective harassing combos, especially in conjunction with Miasma's slow. Definitely max this spell first. The fact that you can spam Twin Fang without end also makes jungling very fast in mid-game - you can take down Golem easily.

Petrifying Gaze - Her ultimate. Petrifying Gaze marks a cone-shaped area in which Cassiopeia delivers damage to all enemies in the area. Enemies facing Cassiopeia are stunned for a short duration while enemies facing away are slowed. Petrifying Gaze is extremely effective during team fights, as you can disable their entire team for a few seconds. In conjunction with ultimates from Miss Fortune or Fiddlesticks, you can deal some devastating damage.



Cassiopeia lacks a reliable escape mechanism. When I decided on summoner spells, I kept this fact in mind.

Flash - Useful for positioning your ultimate and for getting away as well. You can chase with Flash as well as throw off chasers.

Ghost - As a DPS champ, there are moments when smart enemies will retreat and you cannot kill them. Ghost gives you the speed to catch up, snare them with Miasma, and go in for the kill with your Twin Fang.


Exhaust - When Flash gets removed, I'm switching to Ghost+Exhaust. The crowd control is useful, but better is the ability to keep them in a small area while you spam your Q and E, dealing insane DPS. This is also usable now if you don't feel like using Flash.

Ignite - Useful for popping in on an enemy at half health and surprising them with how much damage you're suddenly dealing to them. Very useful early game for first blood and subsequent kills on your mid laning enemy.

Cleanse - Useful for escaping ganks and teamfights. However, as a caster, you should be in the back, far enough away from crowd control that you won't need this spell.

Teleport - A considerable spell if you want the extra mobility. Good for defending towers as well as doing a surprise push.




Greater Marks of Insight give you an extra 8.5 Magic Penetration early game, which gives you an edge when it comes to minion kills with your Q or harass with your E.

Greater Seals of Clarity are extremely helpful in keeping your mana up throughout the game. While you won't have a problem once you get your Archangel's Staff, you may early game, so these runes help you survive that phase while not having to recall back often.

Greater Glyphs of Focus reduce your cooldowns early game - an extra 6% cooldown on your Twin Fang literally translates to an extra 6% damage, since you'll be spamming it that much more. They also pay off late game, as combined with Frozen Heart, you reach almost 31% cooldown reduction - factor in masteries and you're at the 40% cap on the nose.

Greater Quints of Potency are the last runes in a line-up designed to give you an early-game advantage in middle. Your spells will all do more damage, making it easier to nab first blood.


I run the standard caster 9/0/21 mastery set, taking improved magic penetration and cooldowns in the offense line. In utility, I nab improved Ghost and Flash while also getting increased experience, speed, cooldowns, mana regen, and neutral monster buff duration. Top it all off with Presence of the Master, reducing your Ghost cooldown to just under 3 minutes (178.5 seconds) and your Flash cooldown to 191 seconds.




My rationale is exactly the same as user SixSonatas regarding his Taric guide - here's a direct quote from his build that relates exactly to my thoughts on Cassiopeia:

"This item sequence allows you to gain amazing lane presence while almost never having to go back to replenish your MP after Tear of the Goddess is built, which is ASAP in my build order. Also, note that when building items, I have a lot of items that provide CDR. CDR maxes out at 40% and works additively! Keep that in mind when building the additional items. Sight WardSight Ward is a crucial item to avoid ganks - set one up between levels 3-5 to avoid ganks since that's when a good mid or jungler will probably approach you."


So out of the gate, you want to rush a Tear of the Goddess. With the frequency that you spam Twin Fang and the mana you eat up, you'll absolutely need this item to keep your mana pool at a high level. So get a Meki Pendant and two Health Potions to increase your laning duration. On your first trip back, get your Tear of the Goddess and buy Boots of Speed, if possible. Finish your Sorcerer's Shoes later.

Next, instead of going straight for the AA staff, get a Rylai's Crystal Scepter. The additional health on top of the ability power helps, but the real appeal here is that every Twin Fang you throw becomes a snare as well, making chasing and killing easy. Then, finish your Archangel's Staff.

At that point, I prefer to get some survivability items as the other team has probably wised up and is now focusing me in team fights - get a Banshee's Veil if you're faced with mostly magical damage; a Frozen Heart if it's mostly physical. Ideally, you will get both in a single game.

Top it off with the creme de la creme of spellcasters - Rabadon's Deathcap. This item puts you at well over 300 ability power, and the active is useful when being focused down.


Abyssal Scepter - Get this if enemies start getting Magic Resist items. The AP helps and the magic resist reduction supports you as well as your entire team. This gives you some magic resist of your own, as well.

Rod of Ages - Get if you're building a Banshee's Veil but now decide that you don't need the defense and would prefer some beefier spells. Not recommended, but useful if you're seriously winning.

Deathfire Grasp - Not recommended, but if you're not quite level 30 and don't have all of the Glyphs, you won't have 40% cooldown reduction after getting Frozen Heart. If that's the case, you can get Deathfire Grasp to increase your spiking ability as well as putting you comfortably at the 40% CDR cap.

Mercury's Treads - Useful when facing a team containing a lot of crowd control, and you decide you don't need the magic penetration. High-tier boots that are used a lot in higher-ELO play.

Zhonya's Hourglass - Very useful if you feel that you need the survivability and that you're getting focused first. This is by all means a very viable item to get.