Bug: Refunding Pen items still allows 1 attack
I play quite a bit of
and I noticed that if you have this setup for example:

You can buy
, then Refund them, buy
, then refund it, buy
, then obviously refund it, and finish off with
, your next attack(R) will not apply AP from the refunded items, but will fully apply Magic Pen Statistics(Flat and %) even though you do not have the items.
The effect only works for 1 attack. It also wears off, it lasts the exact duration of homeguards, however teleport can get you in lane for it in time. Works on any champion, but Karthus is obviously broken because of this.