How gamebreakingly overpowered would it be
If there was an item that did this?
- +120 AP
- +25 Magic Resist
- UNIQUE Passive: Gain 50% + 5% per level of AP as HP.
I can imagine four insane synergy cases.

If there was an item that did this?
I can imagine four insane synergy cases.

That wouldn't be OP at all. Trust me.

I completely agree. In fact, is there any way we could add an active cc or some magic pen into that?

I don't understand the wording of the passive. Do you mean at level 18 you'd get 18x5% more AP as HP?
Also 
I believe that is what was meant, so a total of 90 + 50 = 140% of ap = hp? It would be a bit too much hp given in late game to be balanced. But as previously stated it looks like a rylais with a terrible passive.
[{quoted}](name=DJ Di0,realm=NA,application-id=3ErqAdtq,discussion-id=QnEkVn5r,comment-id=0002,timestamp=2015-03-15T23:23:46.708+0000)
I don't understand the wording of the passive. Do you mean at level 18 you'd get 18x5% more AP as HP?
Also
yes, that's what i meant
Wouldn't be much different than rylais aside from 25 mr which is shit late game anyways.
[{quoted}](name=j j,realm=NA,application-id=3ErqAdtq,discussion-id=QnEkVn5r,comment-id=0001,timestamp=2015-03-15T23:22:35.015+0000)
Wouldn't be much different than rylais aside from 25 mr which is shit late game anyways.
For most champions, yes, it would be a pretty lackluster item. For others, it could propel their durability to bruiser levels
I don't really understand the point of the thread... How OP would a item that costs 1g and gives +1000 AD +200% AS +100% crit +50% movement speed be?
[{quoted}](name=Awful Volibear,realm=NA,application-id=3ErqAdtq,discussion-id=QnEkVn5r,comment-id=0003,timestamp=2015-03-15T23:25:04.766+0000)
I don't really understand the point of the thread... How OP would a item that costs 1g and gives +1000 AD +200% AS +100% crit +50% movement speed be?
that's a blatantly overtuned item; what i'm talking about is what this item does for slot efficiency. it's cost doesn't matter so much in that case. It would probably cost within the range of 2600-2900
going with that stats, even on a normal champ it'S ~800+hp, it would need to cost 4k+ and it would still be broken. APs would be gods lategame, haveing a free 1k health from the 6th item.... Vlad would run around with 6k hp and still ~800 h in the late, veigar would easily reach 4k, so does cassio Thresh would be a strange builed, you would want the rabbadons to backup the ap, but potentially pretty broken.
if the numbers get toned down, it would only be a rylais without utillity...
I think its a little complicated to have it scaling like that
Just make it 50% of your AP is added to your HP but I also agree that its a little boring, its basically just Rod of Ages or Rylai
Yeah Vlad alone would probably make Riot hesitant to release such an item. If you're talking 140% AP converted to bonus health, Vlad might have what, 600-700 AP lategame? That's almost 1000 bonus health without even considering his passive.