This is a build I have tested and tried out a lot since I have been playing League of Legends. Using this build could be the difference between feeding or getting fed. Now one thing I want to add is this build only works on mana dependent champions. A Rod of Ages is just plain stupid on a champion like Vlad, or Akali. If this build gets enough comments or if people ask, I will make a non-mana dependent page. Thank you and please comment below on opinions. I chose Cass because I love playing her. Also she can be super powerful if played correctly.

P.S. Trolls will be ignored.

I go with Magic Pen Marks, Mana regen per level Seals, and AP per level Glyphs and flat AP Quints. This makes it so you have 21 AP in the very beginning of the match.

Because of the new rune page setup it is better, if you want more damage output. if you want to go more utility then go into that tree.

Items can change for different games, like if you are doing very well in mid lane then you could build a Deathcap first then move onto your other items. If you are doing poorly or, or starting to feed I suggest getting a Rod of Ages first. Now when it comes to Cassiopeia, she can move pretty fast. so dodge and flanking your foes should not be that hard. On almost every champion I play, I get tier 1 boots and 3 Health potions. I believe that it is the best starting items. Then I move onto Rod of Ages. One of my main theories when it comes to LoL is survivability over damage when it comes to building my items. Mainly because you cannot deal damage if you are dead. Also as Cass you will get focused because of your high damage output and your ability to move in and out of combat, but if I am fed, I will get a Deathcap as soon as I can, since that increases your AP by a lot. So, after Rod of Ages and Deathcap I move onto a Rylai's. I get this item because the slowing ability is great for snagging that kill, but it also is great because of the massive amount of health you gain from the giants belt. Then I get a Hourglass because that item also has a needlessly large rod which will give you a lot of AP and it is also nice to have that freeze if you are getting focused and you cannot get out of the fight. It causes confusion, which can help your team push through and win a fight. Now the last item is completely user choice. Some people prefer life steal, so the get a Will of the Ancients, some prefer extra burst so they get a Lichbane. Some people prefer defense and get a Guardian Angels. The last item is completely up to how the match is going and how you are doing. I personally would go with a Will of the Ancients because I prefer spell vamp over burst damage.

This skill sequence is for Cassiopeia only. I chose to get her skill NOXIOUS BLAST at level 1 and max it firstbecause it is a great poke skill and poking is just so much fun. Then I choose to get TWIN FANG at level 2 and max it second because of the cooldown reduction when you have a poison on someone and it deals a great amount of damage. Then I choose MIASMA because of the slow and it makes it easier to apply poison onto the enemy. Then at six I choose PETRIFYING GAZE and max it whenever possible. This is great for catching an opponent off guard. When a Brand or a Veigar comes into to combo you, use your ult to stun then and destroy them, making them wish they did not engage on you.

Summoner spells can be very situation, I usually choose Flash and Ignite because I like the damage and flash is a great way to get out of a sticky situation. I have seen some people choose Flash and Heal or Ghost and Ignite, but over all I choose Flash and Ignite.

I hope this AP build gets some comments and votes soon because Ive had it up for awhile and no comments just views and hopefully this update makes it even better. So for the TL;DR this build is great for surviving and hitting hard. For Cass in general keep them in your poisons and DO NOT INITIATE, this is a problem for AP champs. they like to initiate and they get focused. Thanks for all the comments and I will try to update this as much as possible by reading and testing what you say in your comments.