Why Doesn't Cass Get Magic Pen Per Level?
Something I was thinking about, she can't buy Sorcerer's Shoes like every other mage can, as such she's missing out on 18 Magic Penetration.
To remedy this, why not add to her passive that she gets Magic Penetration equal to her level? It seems a bit unfair that she gets shorted 18 Magic Pen because of 1 random and rather unnecessary interaction.
Probably have the magic pen unlock at level 6 onward so she doesn't feel unfair to play against in the early game. Her passive could then look something like:
Serpentine Grace INNATE: Cassiopeia cannot purchase boots, but instead gains 4 - 72 (based on level) base movement speed, for a total of 332 - 400 (based on level) movement speed. At level 6 Cassiopeia gains "Serpentine Venom". Serpentine Venom: Cassiopeia gains bonus Magic Penetration equal to her level (X).
[X being her gained Magic Penetration]
This is just a thought and shouldn't really be anything game breaking as she will still have lower Magic Resist until level 18 where it equals out.
Let me know what you think and thank you for your time. ^-^
but asking her to get 1 Mpen per level to make up for losing out on 
is fair. Though if its considered to much of a buff or anything, then you could drop her movement speed per level from 4 per level to 3 per level (so she'd still get 54 at level 18 instead of 72). Which is probably why the amount of movement speed she got per level was increased so much, to make up for missing the Mpen or armor/mr from other boots.