I wonder... why has no one tried AP Shen before?
Until now I have used this build:
+ situational item of choice.
Not only do you get a reasonable amount of HP from this items, but you also have enough MPen to be a real threat to squishy targets, not to mention the abyssal/sunfire synergy. And the fact that you can almost permaslow people with Q is nice too ^^
But that's not the most broken part. What makes this strong are the AP scalings - the Shen ult has a 150% one. Oh hey I ult someone... aaaand they have a shield so fat it might be a kayle ult.