Assassin, evolutions? Maybe multiple skillsets? Or a lame-ass shapeshift? Maybe a triple shapeshift? Noone knows!
From what I know how it works is whenver he gains a point in his ultimate the next ability he uses will be permanently upgraded.
That's 3 ultimate ranks so he can upgrade a single ability to full potential and another half or have all abilities upgrades halfway.
If I'm not mistaken his q gains range and on second upgrade additional aa damage
The armor buffs on hit passive component stack higher and ultimately do not disappear when he activates the ability.
And the with upgraded leap he grows wings and leaps further and fully upgraded stuns (not sure) on impact.
From what I know anyway, he's not out yet for some time so who's to say.
About cass, she's my main ap for sure. Although she plays more like an ad with great early but not nearly as devestating late, the way she's all about sustained damage.
Better yet if the ult is well landed you should have no problem dealing with high damage squishy targets (unless they're smart and get qss) and beefy bruisers alike due to the sustained damage potential. Throw in a bit of spellvamp (quints and wota) and low damage bruisers don't stand a chance.
I highly suggest buying rylai sceptre asap on her, it gives her a much needed slow. That and the speed boost on q means you can kite like no tomorrow while laying down the damage.
As a third item It's usually tied between wota and deathcap depending on lineup and how the game goes, I used to buy abyssal sceptre as well but I'm not so sure after its nerf.
Cass is awesome, definatly favorite mage.
I like syndra a lot to but it seems she is simply not viable and in need of buffs. Base dmg on the ult is nice but that's all she has going for her.
Cass' ult on the other hand can be game changing if used correctly.