Inspiration for sustain
Sorcery for scaling
Cassiopeia's Skill Max Order: E → Q → W
Level 1: Hide in top bush and conduct Quinn Cheese. Wait for passive to mark her, then Auto-E-Auto to consume to harrier procs. Cass will retaliate with either Q or E. If she starts Q, run her down for 3 seconds before her second Q comes back. If she starts E, proceed with auto attacks until you proc PTA, then run back in the bush to drop minion aggro.
Level 2: Cass will have Q and E, but you are still stronger. Make sure to land Q and do short trades because Cass will win long trades with her Q. If you miss Q, back off so Cass can't run you down with a big trade.
Level 3-5: Cass will have W, which makes you unable to vault. If she lands W on you, make sure to blind her so she can't hit you. Goal in lane is to bait her W, and if she ever throws it, you have 24 seconds to take control of the lane. Don't let her breathe for these next 24 seconds, hard punish her because you take over trades and lane when its down. Do not play passively, if she wastes this ability then you must punish her. If you walk up she will run away afaid, so you can also zone her off the wave or constantly look for trades against her. If she misses Q, run her down and this will force her to W you, which is fine if you blind her because she cant hit you with her Es if she is blinded, so you will win that trade even when her W is on you.
Level 6+: Quinn's E can make Cass R backwards, if timed correctly, but this is mostly helpful when you are flying at her. In lane, however, just respect her R advantage and try not to get hit by it. If she Rs you and Ws you, you cant vault after R so you're basically dead. Her R range is 825 units, which is much greater than your 525 Auto range, so be careful about positioning, If you can bait out cass W in lane, Cass's R isnt as scary because Once R vanishes, you can Q-E her and run away for free with your W movement speed.
Important Matchup Tip: Use your E, vault, to dodge Cass Q if possible. Dodging her Q with E renders her Es to do much less damage, and it's a 3.5 second cooldown before she gets it back.
Cass matchup is Quinn favoured if you play it correctly.
First, let me make this clear: if you vault Cass the moment before she presses her ult, then Cass will ult backwards because Quinn's vault knocks the target in the opposite direction for a brief second.
This seems difficult to reproduce, but I have learned to recreate this mechanic almost every single time I vs a Cass now.
The reason it isn't as hard as you might think to do is because if you try to engage on cass early, Cass's from every elo's natural instinct is you ult you immediately, and by the time they press it, your E will hit them and make them ult backwards.
If you land blind on Cass in lane, go ham and proc PTA and combo her because class can’t retaliate with her E on you.
If Cass misses a Q in lane, this is your window to engage on her because she relies on that ability to spam her E.
Next, Cass W screws over your E since you are grounded, so the objective is to bait Cass W whenever you can.
If her W is down, you are free to use vault to combo her if it’s Pre-6.
Cass has lots of healing and will beat you up if she lands Q on you, so try your best to dodge her Qs.
Utilize the bushes in this lane because Cass is ranged, and the only way she can trade if you walk in the bush is with her Qs, which are hard to land if you're out of vision.
Forcing her to miss Q allows an opportunity for you to run her down.