Hello! I'm a master tier Cassiopeia OTP who has been playing her since I began playing back in season 9, I also occasionally stream at Twitch.tv/zeusman00 . Since then she's gone through many metas and variations of builds, and I confidently can say this is definitely the strongest she has been in a long time. I hope you can find this guide helpful and informational as this is the first one I've made!

Cassiopeia right now is an incredibly strong midlaner in the meta due the popularity of bruisers and tanks in the meta and her ability to peel herself while putting out high amounts of dps, as well as her counters being not as strong in this current meta. The items also very much fit the needs that she has with Rod of Ages giving her a large amount of health and her ability to abuse the passive for incredible amounts of sustain. Rylai's Crystal Scepter and Archangel's Staff are also incredibly cheap right now which helps give her that 3 item powerspike she really needs in the game. After these 3 items she becomes incredibly tanky and can afford to go hybrid and build tank like Gargoyle Stoneplate, Frozen Heart, or even Force of Nature while still being relevant within the game.

The first step to learning how to play Cassio properly is to learn what her abilities do, and how they work!

	INNATE: Cassiopeia gains 4 − 72 (based on level) bonus movement speed, but she cannot purchase Boots.
	ACTIVE: Cassiopeia creates a blast at the target location that explodes after a 0.4-second delay. Enemies within the blast are poisoned for 3 seconds, taking magic damage every second over the duration. If Noxious Blast hits an enemy Champion, Cassiopeia gains bonus movement speed that decays over 3 seconds.
	ACTIVE: Cassiopeia spews forth 8 bolts of venom in an arc at the target location, creating toxic clouds at the area for 5 seconds. Enemies within the clouds are poisoned to take magic damage every second and become grounded and slowed by an amount that decays over the area's duration.
	ACTIVE: Cassiopeia launches her fangs at the target enemy that deal 52 − 120 (based on level) (+ 10% AP) magic damage. If this kills the target, Twin Fang's Mana icon mana cost is refunded. Against a poisoned target, Twin Fang deals bonus magic damage and heals Cassiopeia. The heal is reduced by 75% against minions and small and medium monsters.

Lets start with runes, there are 2 main sets of runes that I recommend taking, I'll also go into detail about other secondary rune choices that can be useful on Cassiopeia as well

This set of runes I recommend for lanes that aren't control mage or artillery mage lanes

	Conqueror is the standard rune for skirmishing and for power on Cassiopeia. This rune allows you to gain power for each auto attack and ability that you cast. I highly recommend going this keystone if you are facing a bruiser/fighter or a tank in lane, or if enemy team is majority of these classes as well		Transcendence is almost a necessity on Cassio with Rod of Ages being the prominent and strongest build on her at the moment. This rune helps to make up for the ability haste that you don't get from Rod of Ages, this is also a very conveinent rune because of its ability to reduce basic ability cooldowns by 20% on a takedown, this means that if you are fighting multiple people and you get a takedown, you can quickly turn around and use Noxious Blast on another enemy in order to keep the DPS up
	Presence of Mind is an extremely vital rune for Cassiopeia due to how mana hungry she is as a champion. During fights she can run out of mana incredibly fast due to the cooldown and mana cost of Twin Fang, by taking this rune, this allows her to regenerate mana in lane simply by auto attacking or using an ability on an opponent, but also in the middle of team fights, every time you score a takedown or an assist, you regenerate 15% of your maximum mana, allowing you to stay in the fight for even longer		Waterwalking is one of my personal favorite runes to run on Cassiopeia while playing midlane. Due to the fact you can easily gain mid prio into many of her matchups, this rune helps in making roaming a little easier by granting you movemenet speed within the river and even an AP boost in the river as well which helps out quite a bit in early game scuttle fights. This rune is also effective in mid-late laning phase when you are looking for a roam on one of the sidelanes, it helps with zooming down to that lane and making a gank happen a couple of seconds sooner
	Legend: Tenacityis an almost essential rune for Cassio to take, mostly due to the fact that she is not able to purchase boots in order to gain that tenacity. Cassio is a very slippery champion who heavily relies on her movement more so than most other champions. Without having access to boots she doesn't have another way to gain that tenacity which she needs so much.
	Last Stand is a rune that synergizes incredibly well with Cassiopeia and the items that she builds due to the shields that she has access to. With Seraph's Embrace and Gargoyle Stoneplate being core items for her kit, it makes it incredibly hard to kill her after she drops below 30% health due to the shields these items provide

This set of runes I recommend for control mage or artillery mage lanes due to how difficult it is to make extended trades with them

	Phase Rush is extremely helpful in these lanes because of how difficult it is to take extended trades with these mages because of their range. Phase Rush allows you to land a Noxious Blast followed up by 1 or 2 Twin Fang attacks, or even another Noxious Blastgranting you a large boost of movemement speed that can be used to chase and catch up to the enemy to put in a little bit more damage. This rune also works as a defensive rune, if you get into a sticky situation, you can drop 3 quick abilities and use the movement speed to get to safety		Presence of Mind for same reason as stated in above rune set
	Manaflow Band is a very useful rune due to the fact that Cassiopeia is a very mana hungry champion by nature. This rune allows her to gain an additional 250 maximum mana as well as helping slightly with mana regeneration after reaching maximum stacks (1% max mana regen per 5 seconds after reaching max stacks)		Legend: Tenacity for the same reason as state in previous rune set
	Transcendence for same reason as stated in above rune set
	Waterwalking for same reason as stated in above rune set

These following runes are alternate secondary runes that work as substitutions for the runes I spoke of above

Sorcery Tree

Scorch is good in lanes where you think you can confidently land a lot of Q's on the enemy and poke them down in lane, very effective if you just want to take quick safe trades

Gathering Storm is an amazing rune for games where you want to sit back and scale, Cassiopeia scales really well into the late game so this rune helps amplify that late game potential that she has

Resolve Tree

	Conditioning is a rune used for scaling post 12 mintues, this rune grants you an additional 8 Armor and MR while also increasing your overall resistances by an additional 3%, which only increases the value of Gargoyle Stoneplate even further		Second Wind is a helpful rune where you can be poked constantly, certain matchups such as Viktor and Orianna I have found this rune to be extremely helpful in
	Bone Plating is an effective rune against champions who have a strong all in potential, it helps to cushion the blows while you can trade right back with them a little extra		Overgrowth is a scaling rune that grants you 3 extra health for every monster or enemy minion that has died near you, on top of that after absorbing 120 units worth, your maximum health is increased by an addition 3.5% health which only adds to your late game tankiness

These are the summoners that I recommend using in lane, and what I find them useful for

	Flash is the default rune that you take practically 100% of the time due to it's ability to allow you to quickly get out of a potentially sticky situation, or even help you to avoid being hit by cc spells. Another use for Flash can be to engage on enemies whether you want to extend the range of your R, or reach a slightly out of range enemy		Teleport is one of the safest and strongest runes for Cassiopeia due to it's ability to allow you to recall early in order to gain an item advantage in the early game without sacrificing a large amount of your laning pressure. Another advantage is in the late game, this rune allows you to split push and draw pressure safely as you can still Teleport into fights to join into the fights and assist on objectives
	Ghost is a useful rune into lanes where you have heavy solo kill pressure on the opponent as it can be used to draw out a flash in the early-mid game, this rune also allows for more successful roams due to the movespeed it grants, allowing you to reach these fights sooner. This rune also scales exceptionally into the late game and shines incredibly well in team fights due to the fact that it helps in letting you skirt around the edge of the fight and dodge skill shots all while getting additional ghosting time for each takedown you score		Ignite is useful in certain lanes where the enemy has strong mid-fight heals, or getting an early lead allows Cassiopeia to take full control of the lane and snowball hard into the late game. Ex. Vladimir, Sylas, LeBlanc, etc
	Exhaust is a very safe summoner spell to take, especially into high aggression lanes where Cassiopeia is not able to match the enemy's damage especially in the early game. This summoner allows you to almost fully shut down the enemy's engage or burst and come out on top of bad trades Ex. Yasuo, Irelia, Akshan, Tristana, etc		Barrier is another form of a safety summoner spell that you can take against champions who can burst a large amount of your healthbar. I generally prefer this rune into assassins because of how difficult it can be to exhaust them sometimes Ex: Fizz, Talon, Qiyana, etc
	Cleanse is very helpful in lanes where the enemy has a reliable form of cc and the enemy jungler can capitalize on this. Highly recommended against champions such as Annie, Zoe, and Twisted Fate

Below are the list of items that work very well for Cassiopeia as well as what her core build generally is, as well as item variations and why they are good

The following 4 items, are the general core items of Cassiopeia's kit

	1. Rod of Ages is the general go to mythic for Cassiopeia due to the large amount of stats that it gives to her, as well as the extra level that you gain from the passive after the item reaches 10 stacks. Cassiopeia is also able to heavily abuse the passive sustain this item gives, due to how fast she can burn through mana, allowing her to heal herself a substantial amount during fights.		2. Rylai's Crystal Scepter is an absolutely essential item for Cassiopeia due to the large amount of health that it grants, along with the slow it applies when you land your abilities onto an enemy. This slow synergizes very well with Noxious Blast as you gain movement speed when you land this ability onto an enemy champion, this allows Cassiopeia to chase after and make quick picks on enemy champions as well as allowing her to self peel and kite when she is in a sticky situation. Another use of the slow is for team fights which helps your team make picks if an enemy steps up too far and gets hit by an ability. This item also has a much easier build path to follow than Archangel's Staff in the early game, making it much easier to go this item 2nd instead.
	3. Seraph's Embrace is an absolutely essential item for Cassiopeia due to the large amount of mana and AP that it grants, alongside it's passive ability. The lifeline shield is a very powerful tool that can save Cassiopeia in many close fights and can allow her to come out on top.		4. Gargoyle Stoneplate is an absolutely incredible item for Cassiopeia due to the fact that her build contains a large amount of health in it already which synergizes with this item's active. This item also grants a large amount of resistances with bonus resistance for each enemy champion that is targetting Cassiopeia, this means that with this item you can very easily become a very durable snek. Another upside to this item is the fact that Cassiopeia already puts out a large amount of dps due to her kit, so building this item allows her to stay in the fight even longer and output more dps

The following items are items that work as 5th or 6th items, or can also be slotted in as subsitutes according to game state

	Void Staff is generally the best item to build 5th because of how high MR tends to get at this point in the game, and especially if there is any sort of MR items being built, this helps let you do damage again to these players. This item can also be slotted in earlier in the build if the enemy team is starting to heavily itemize MR.		Cosmic Drive is a great item for [cassiopeia]] to build, largely due to the move speed and ability haste that is granted from this item. The ability haste is valuable from this item as it makes her Twin Fang feel a lot smoother and almost feel as if you are a machine gun. The move speed is also a very helpful stat this item provides as Cassiopeia heavily benefits from this movement speed boost and it allows you to kite out fights beautifully.
	Rabadon's Deathcap is a very powerful item in the later stages of the game due to the large base amount of ability power it provides, alongside the passive amplifying your AP by an additional 35%		Demonic Embrace is a good item for giving you extra health and durability in the late game. I only recommend this item if you think you need the extra health in fights in order to stay alive. This item is not meant to be built for damage, this is a common trap that many Cassiopeia players fall for
	Mejai's Soulstealer is a good item if you are able to avoid dying and keep snowballing your lead. This item is a very high risk, high reward item as it provides a large amount of AP as well as giving a 10% movespeed boost if you have 10 or more stacks.		Liandry's Torment Is a Mythic item replacement for Rod of Ages. This item is a good item to build if your team is able to peal you throughout the game. This item is a much higher damage option than Rod of Ages but it leaves you much squisher and vulnerable to damage.
	Frozen Heart is a great alternative to Gargoyle Stoneplate in games where the enemy has drafted full AD and there is no AP threat. The base armor this item grants is the highest in the game and it also gives a substantial amount of mana that can be applied towards the Seraph's Embrace shield. On top of these factors, both of the passives are incredibly strong, especially with Rock Solid passive scaling off of bonus health, which Cassio builds a lot of.		Force of Nature is a great alternative for Gargoyle Stoneplate in games where there is a large amount of AP damage on the enemy team with little to no AD threat present. The movement speed and up to 25% magic reduction on this item make it the #1 best item for Cassiopeia to buy in cases where she needs strictly MR
	Everfrost is another Mythic item replacement for Rod of Ages. This item is generally good for high mobility assassins who can easily avoid your abilities and Miasma.

Despite Cassiopeia being one of the strongest late game scalers, she has an impressively strong laning phase. She can be considered a lane bully. Generally to start your laning phase, you will want to start off with a Tear of the Goddess. A common bait item many people will buy on Cassiopeia is Doran's Ring, this item is extremely bait to buy at the start of the game as you will have next to no mana in order to lane properly.

While laning you want to look to make quick trades and poke enemies with your Q. If the enemy is a melee champ you want to look to poke them with auto attacks as well in order to proc your Presence of Mind rune and regen mana. Look to gain level 2 advantage in order to pressure and make an early trade with the opposing laner to gain lane prio and slow push into the tower in order to look to assist your jungler. While making early game trades, you want to weave auto attacks in between your Twin Fang attacks in order to help build conqueror stacks and maximize dps. This is very important mechanic to take advantage as you have a very small mana pool in the early game.

Look to farm for 750 gold and get a recall off for a Doran's Ring and a Dark Seal (I only recommend this method if you are building Rod of Ages). After you have these 2 items, you become an incredibly strong and durable early game champion. You can start to look to take heavier trades with Noxious Blast and Twin Fang as you will start to do a substantial amount of damage now. From here on you can look to bully the enemy laner or look to make roams with the jungler because you can gain lane prio easily a majority of the time. I generally like to take Waterwalking as the move speed helps me with roaming and not missing as much cs and exp as usual.

Cassiopeia can be quite strong while ganking sidelanes due to her Miasma, with the large AOE of this ability, it makes ganking lanes incredibly easy while making it hard for enemy champions to escape. She is also very useful for tower dives as her Miasma covers a large portion of the tower range.

During the mid to late game, Cassiopeia is incredibly strong in the side lanes and in team fights. In team fights Cassiopeia can play a very strong role in zoning and creating an area of denial with her Miasma. Another reason Cassiopeia is very strong in team fights is because of the slows she applies with Rylai's Crystal Scepter allowing your team to make easy picks on enemies that walk too far up in team fights, or chase down the enemy team in general. Cassiopeia thrives in front to back teamfights because of how efficiently she can shred through healthbars.

In the side lane, Cassiopeia is incredibly strong due to her strong 1v1 and outplay potential. Many times you can draw pressure from multiple champs to come botlane and your team can use this pressure in order to capture objectives, or push another lane for a tower.

• Miasma can stop any dashes from being cast, it can even stop Ziggs from using his Satchel Charge from jumping away But it will not stop Jarvan IV from using his EQ combo.
• Any other form of poison from other champions will allow Twin Fang to apply is bonus poison damage.
• Cassiopeia can cast Petrifying Gaze and Flash after casting to extend the ult, or adjust her positioning.
• Noxious Blast ignores Malzahar's shield passive and will still proc poison and move speed bonus
• Many times when a champion uses their gap closing ability to reach you, instead of attempting to Miasma to prevent the dash, use it on top of yourself so they are slowed and you can force them into a less favorable trade
• While chasing an opponent, it's not always best to start spamming your Twin Fang as soon as you land Noxious Blast, instead use the movement speed granted by Noxious Blast to catch up to the opponent and then start using Twin Fang. This can sometimes allow you to get more casts off.

Thank you for taking time to read my guide on Cassiopeia, I will be looking to update this frequently as well. This is my first time making a guide so I really hope it was helpful to everyone reading it and you can all take this into your games and improve on the snek! I do stream on twitch fairly frequently so if you have any questions you can also pop by there and ask me them there as well!