Cassiopeia wins fights by keeping targets poisoned and repeating Twin Fang on a short cooldown. If you understand how her poison windows work, you can plan trades, chases, and teamfights with less guesswork.

This guide sticks to the mechanics and advice in the Cassiopeia information you provided, including ability details, item options, rune notes, and known interactions.

How Cassiopeia’s Kit Fits Together

Cassiopeia is built around one loop: apply poison with Noxious Blast (Q) or Miasma (W), then spam Twin Fang (E) for enhanced damage and self-healing.

Her ultimate, Petrifying Gaze (R), gives her a moment where enemies must choose between turning away (slow) or facing her (stun). That choice can decide fights before they start.

Serpentine Grace (Passive): Movement Speed, No Boots

Serpentine Grace gives Cassiopeia scaling bonus movement speed based on level, and she cannot buy boots. This shapes her builds because she can still reach a normal movement speed range without spending gold on boot items.

A practical side effect: the Magical Footwear rune can’t function, so it gets replaced by Triple Tonic.

Noxious Blast (Q): Delayed Zone, Poison Window, Speed Burst

What it does

Noxious Blast creates a blast at a target location and detonates after a short delay. Enemies inside get poisoned for 3 seconds and take magic damage over time.

If Q hits an enemy champion, Cassiopeia gains bonus movement speed that decays over 3 seconds. That speed matters for chasing, spacing, and dodging skillshots.

Timing and damage details

Q’s damage is split into ticks, and the tooltip-style displayed damage can differ from the true total because tick damage is calculated with rounding rules. The notes you provided also mention a known bug case where Q may deal 1 less damage at precisely 20 or 40 bonus AP, separate from rounding.

How to land it more often

Q has a delay, so aim where the enemy will be, not where they are. Use Q on moments when they have to stand still to last-hit.

You can also cast Q into brush to check for enemies. If you see the movement speed buff icon from hitting a champion, you know someone is there.

Miasma (W): Grounding, Decaying Slow, Control Tool

What it does

Miasma fires venom bolts in an arc, creating toxic clouds for 5 seconds. Enemies inside take damage over time, get grounded, and get slowed with a slow that decays across the area’s duration.

W also has a casting rule: if you cast beyond max range, it casts at max range instead.

Cleanse rules and special interactions

The notes mark the Grounded and Slow debuffs as non-dispellable by most cleanses. They can be removed by effects that grant immunity to the debuff type, such as Olaf’s Ragnarok.

There are also projectile interactions called out: Wind Wall blocks the part of Miasma it destroys, and spell shields can interact with it in the way described in your notes.

Tick quirks (important for expectations)

Your notes include specific tick behavior: Miasma’s damage uses ticks, and it may total slightly less than a simple “per second × duration” expectation due to its tick count. They also note a bug where it sometimes inflicts fewer ticks than expected.

Twin Fang (E): The Damage Engine

Baseline effect

Twin Fang hits a target enemy for magic damage on a very short cooldown. If it kills the target, it refunds the mana cost.

This is why Cass can keep casting in lane if she last-hits with E and manages her mana well.

Poisoned target bonus: damage plus healing

Against a poisoned target, Twin Fang deals bonus magic damage and heals Cassiopeia. The heal is heavily reduced against minions and small/medium monsters.

Most of Cassiopeia’s real threat comes from making sure the target stays poisoned so E stays in its stronger mode.

A key mechanical detail with Q

If a Noxious Blast is already in flight and hasn’t detonated yet, Twin Fang will wait for Q to explode before it deals damage when it reaches the target. That matters when you’re trying to chain Q into fast E casts.

Petrifying Gaze (R): Slow or Stun Based on Facing

What it does

Petrifying Gaze damages enemies in a cone and slows them for 2 seconds. If enemies are facing Cassiopeia, the slow becomes a stun for the same duration.

This creates clear counterplay: if you turn away during the cast, you aim to take only the slow.

Facing and cast behavior

Your notes include several important mechanics:
Cassiopeia turns to face the target direction over the cast time, and the ability casts from where she is at the end of the cast time. Knockbacks that change her facing during the cast can change the target direction.

They also note special behavior for champions whose animations lock facing or spin, and that Lucian’s The Culling is treated differently for facing direction.

How to Trade and Win Lanes with Cassiopeia

Cassiopeia can harass through the whole lane phase because Q and W can zone from range. Still, she runs into a real limit: early mana.

Use Q to tag a champion for the movement speed boost, then reposition for follow-up. If you land poison, E becomes your main tool and you can keep hitting while the poison lasts.

Brush can help you trade with less risk from minion aggro, since your notes state Q in brush does not reveal Cassiopeia.

Chasing, Escaping, and Setting Up Kills

When chasing, use Q on the enemy champion to speed yourself up, and use W to slow them down. The slow decays, so placement matters; try to place it where they must walk, not where they are.

When fleeing, W can deny dashes and mobility by grounding enemies. That is one reason Cass can survive situations that would normally kill a mage with no dash.

Teamfights: Picking the Right Moment for R

Petrifying Gaze is safest when multiple enemies are likely to keep facing you. A busy teamfight helps, because enemies often focus on your teammates and can’t react fast enough to turn.

If you stun more than one target, you can swing a fight hard. Follow R with W and Q to lock the area, then E the highest-value poisoned target until the window ends.

Items for Cassiopeia (Based on the Provided List)

Your provided item plan highlights mana and sustained casting first.

Start with Doran’s Ring, Health Potion, and Warding Totem, then aim for an early Tear of the Goddess. Tear helps with heavy casting demands, and it naturally upgrades into Archangel’s Staff and later Seraph’s Embrace for a mana-to-power path and survivability shield value as described in your notes.

Core and common options in your list include Rylai’s Crystal Scepter, Rabadon’s Deathcap, Void Staff, and Morellonomicon. Situational options listed include Zhonya’s Hourglass, Banshee’s Veil, and Luden’s Echo.

Runes (Based on the Provided Notes)

Phase Rush

Phase Rush activates quickly due to rapid spellcasting and helps you reposition after short trades or stay in range to keep E going.

Summon Aery

Summon Aery adds consistent extra damage early. Your notes also point out a limit: Cassiopeia mostly has Miasma as a more reliable multi-proc tool, and Aery’s scaling falls off later.

Supporting rune notes

Your notes list options like Manaflow Band, Celerity, and Gathering Storm or Scorch, plus sustain tools such as Taste of Blood and the (historical) mention of Ravenous Hunter for in-fight sustain tied to Twin Fang’s single-target value. They also mention Biscuit Delivery, Minion Dematerializer, and Time Warp Tonic as lane and mana support ideas.

Playing Against Cassiopeia: What Actually Stops Her

Cassiopeia mostly deals magic damage, so magic resistance reduces her output. Your notes single out Adaptive Helm as a strong answer against repeated Twin Fang casts.

The simplest fight plan is to avoid getting poisoned. If you dodge Q and avoid standing in W, you cut off the E bonus damage and healing that drives her trades.

Assassins like Zed, Talon, and Fizz can be strong against Cassiopeia early, especially before she has R. Your notes call out Zed and Fizz as top threats because they can avoid the impact of Petrifying Gaze with their kits, while also noting that these tools can’t be used if they are standing on Miasma. Long-range mages like Vel’Koz, Lux, and Xerath can also pressure her because Cass struggles to close distance without mobility.

Quick checklist for clean Cassiopeia fights

• Land Q with a lead on movement, then use the speed to space for E casts.
• Use W where enemies must walk to force grounded and slow value.
• Treat E as your main damage tool only when poison is active.
• Use R when enemies are likely to keep facing you (busy fights, tight areas).
• If you’re against Cassiopeia, turn away on R to take slow instead of stun.

Closing takeaway

Cassiopeia rewards precision and punishes hesitation. If you track poison uptime and manage your early mana, your fights become repeatable: poison, E chain, reset, and take space with W and R when the enemy tries to force a decision.

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