How do shields work?
Are shields affected by pre or post mitigation dmg? For instance, kassadin has 15% magic reduction, and can get a magic shield. Say he's damaged with 100 magic damage. Does this damage apply to the shield as 85 damage or 100? If you think about it technically, a shield would be outside of the person's runic armor, so it makes sense that it would take true damage.
Also, does true damage affect shields? In theory, true damage would apply directly to the health of the enemy, but I'm not so sure.