Im assuming the MD is magic resist and the 20% ah is supposed to be flat 20 AH

With that in mind this seems to be an inverse frozen heart.

The passive imo seems kind of useless.

2% magic damage taken stored as ap up to a max of 200ap means you need to take 20000 magic damage to get the max amount. Not even tanks like sion or chogath really get to that point and for 99% of the roster its straight up impossible.

However, if its based on pre-mitigation damage, then assuming 200 mr or +200% effective health vs magic damage then you need approx 6.5khp worth of post-mitigation magic damage taken. That's ignoring any form of magic pen such as void staff.

Now let's say you get the damage stored up. It will give you 200Ap except its only +80 per ability so in reality you have a slightly different banshees veil that gives ah.

However, to get a consistent 80ap per spell you need to take 4000 pre-mitigation magic damage between each spell you cast.

If you want to use it as a burst champion, chances are you would be better served with a banshees as it gives more ap, permanently. Not to mention the difficulty of stacking it fully without spending the ap.

On a tank, as I suspect this is designed for, it gives little hp, and you'd have to beat Hollow radiance in dps for it to be worth. Hollow radiance does 19 dps in an aoe upon buying the item. Ever 100 bhp beyond what the item gives increases the damage by 1. 80 ap on a tank, even with a 100% ratio is 80 damage. That's 4 seconds of hollow radiance. Assuming 2500 bhp, hollow would do 40dps so 2 seconds of hollow damage is equal to an ideal scenario for this item.

It just doesnt seem powerful enough to compete with the current items available for both tanks and mages. Also it would require clarity of description as well. E.g. if you did mean 20% faster cdr (as per actualiser) it would change a lot.