Item Ideas: Gem of Resistance and The Endostone
Gem of Resistance: +300 Health UNIQUE PASSIVE: Causes you to take 10% reduced physical damage and magic damage.
Cost: 1350(200)
Components: 


The Endostone: +600 Health UNIQUE PASSIVE: Causes you to take 16.67% reduced physical damage and magic damage.
Cost: 2700(950)
Components: Gem of Resistance, 
Not sure if this is a good idea or a bad idea. The idea is that it would be calculated after armor and magic resistance, and since it's not technically armor/magic resist, it wouldn't be affected by armor/magic pen.