Cassiopeia/Strategy

Skill usage

 * Don't hesitate to spam your spells since makes each additional cast cheaper.  does not require a target, so maintaining your 5 stacks is easy with a decent-sized mana pool.
 * Try to acquire 5 stacks of before casting  to lower its mana cost significantly.
 * is a great harasser in all stages of the game. All three of her basic abilities, especially, can be used constantly in lane to zone, capable of dealing huge amounts of damage over time at a safe distance.
 * has a slight delay; lead your enemy when targeting with to ensure the hit, or use it on them when they will have to stand still to last-hit.
 * Using in the brush does not reveal, so when in the side lanes, use the brush to your advantage to harass with little to no retaliation from enemy minions.
 * When chasing/fleeing, be sure to use your on an enemy champion to speed yourself up, and  to slow them down.
 * Using in the middle of the lane when enemy minions are coming will slow them and deal some damage giving advantage to your minions, this tactic is best used in pushes as intentionally pushing your lane during the laning phase opens yourself up to ganks.
 * Since grants vision over the area affected, it can be used to check brush.
 * can also be used to check brush, as it gives you a movement speed bonus (and a buff icon) if an enemy is hit. If you cast it in a brush, and notice the buff icon, you know that an enemy is there.
 * becomes extremely powerful if the target is poisoned, allowing you to deal out large amounts of damage with its low conditional cooldown.
 * It is very highly recommended to smart cast, as it will make it much easier to land the maximum amount of allowed by the duration of your poison effects.
 * If the situation is favorable, try to cast while directly on top of your target, as 's reduced cooldown begins when the poisoned target is hit and not on spellcast.
 * Due to having the potential to be constantly refreshed, don't be afraid to target durable melee champions if necessary. Unlike many other mages that rely on burst damage,  and her  can realistically cut through tough enemies with time, accuracy, and enough mana.
 * Try to use offensively, and usually against more than one target. That said, it can also be used when being ganked to escape enemies.
 * It is, however, safest to use it when a teamfight has happened. The enemy will be less likely to manage to turn around with their attention split amongst five champions - and more likely to all be facing you since that is largely required to fight your team.
 * Using followed by,  and  can turn most 1v1 fights and mid game turret dives in your favor.
 * also allows to be a very strong anti-ganker. Simply casting it when your lane opponent and the enemy ganker are in range, then bursting down the weaker one with your combo can turn the 2v1 into a 1v1. This tactic is only effective when your  stuns both targets.

Build usage

 * Buying along with using  on a poisoned enemy gives her much more chasing potential, but don't forget hit enemy with  from time-to-time to refresh the poison and the movement speed bonus for yourself.
 * However, be aware that only slows by 15% with a . This is intentional due to the mechanics having a potential to perma-slow an enemy, according to the developers.
 * Also, plus  adds a very powerful slow to your enemies, giving  more time to chase and land  easily.
 * works fine on if enough enemies have a high amount of magic resistance, as the potential low-cooldown and damage on  lets  be less stringent in choosing targets compared to other mages.
 * Buy spell vamp items like to quickly restore health when hitting poisoned targets with.
 * A is a perfect early game item for  allowing her to spam her spells more often with the extra mana and some health for survivability. This can then build offensively into an early  or a more defensive.
 * Even if she doesn't need the mana, getting a and then upgrading it into an  will greatly increase  ability power.
 * Avoid building cooldown reduction. Because 's damage tick is constant and can only be reapplied, and using on a poisoned enemy reduces the cooldown to 0.5 seconds (which cannot be further reduced by CDR),  does not gain the significant benefit from CDR as other mages do.
 * Therefore, will be the major purchase for when you want more damage as.

Countering

 * If you can predict when will use  such as at the beginning of a fight or at the end, you can avoid the 2 second stun.
 * You will hear gasp before she activates  (.65 casting time), so you have a brief moment to react to.
 * relies heavily on landing so that  and  are unavoiable.
 * When dueling her she will put  right on you, despite the constant damage from it the time needed to move out will let her spam  to death.It's better to stay in the venom and outburst her
 * Strong spellvamper's like ,  and  can easyly output her DoT damage enoght to defeat her
 * Even with her passive, avoiding several of her abilites (better said which is very predictable) will quickly lead to mana problems.
 * lacks a powerful instant nuke apart from, other  mages who can nuke potently or disabling her like  or  can effectibly counter her mid-late game
 * has excelent range on and as it's main harrassing tool, outranging her is highly benefitial , mages like  and  have a clear advantange.
 * This mages can also outburst her if done correctly.
 * is a very powerful harasser. allows her to give her lane opponnent a hard time, but also be wary for, as it can set you up for ganks, make landing  or especially  extremely easy, or zone you from minions very effectively. Buying  is a good and cheap way to limit her harassment.
 * is extremely proficient at 1v1 fights, having the most sustained damage of all mages (maybe only matched by ). Therefore it is not recommended to engage her alone. Since has very high ability power scalings, she remains a constant threat to AD carries late game, since if she lands her ultimate, she can easily kill an AD carry without resistances within the 2 second stun  provides her.
 * Champions who can outmatch her sustained damage but also survive the 2 second stun like , ,  or  can potencially duel and kill her.
 * Due to and,  is very powerful at kiting. If she gets  she will be almost impossible to reach if played correctly; do not engage her with a champion without strong gap closers or excelent ranges while also being able to withstand her damage in a 1v1 fight.
 * Avoiding her and  is critical for your survival, as they deal heavy DoT, and being poisoned allows  to spam her  on you.
 * Also, avoid being hit by other champion poisons such as, and /, which will also allow  to spam her.

Champion Spotlight
http://www.youtube.com/watch?v=neQNvEyuhPU