New item for Hybrids: Magical Sword (Change the name later)
Magical Sword: +25 Attack Damage +40 Ability Power UNIQUE Passive: 15% Armor Penetration 15% Magic Penetration
UNIQUE Passive: Your next ability will deal a bonus (0-1% based on the target's current HP) true damage for every 12 Armor/MR the target has, but increase their resistances by 25% for the next 2.5 seconds. Deals a minimum of 10 (+5% AP) (+8% AD) damage. (8 second cooldown)
How it works: The percent is equal to the target's current HP% divided by 100.
So if Malphite has 300 armor and 100 MR, and is at 50% HP your ability will deal a bonus 0.5% true damage based on his resistances (400 total / 12 per 0.5% dmg) = 33.3% bonus true damage, but then Malphite will gain 75 armor and 25 MR for 2.5 seconds.
Just a thought.
Builds out of 
+ 
+ 800 gold = 2,525 gold.
