I know it can't be reduced by exhaust or anything but does it deal more damage to units or champs that are debuffed to take bonus damage from enemies?
If so does that mean masteries increase true damage as well?
Zane Zephyr1 votesNope, it's not able to be amplified anymore
Ok sure but why1 votestrue damage, is true damage, is true damage
if it could be altered by mere masteries, it wouldn't be true damage
it would be false damage
Cro0031 votesTrue Damage is a third damage type in addition to physical and magical damage. It looks like Riot changed how the following works per the Wiki: True Damage and Magic Penetration
For example, you will do bonus damage when your armor or magic piercing is greater than the specific resistances of your opponent.
For example, 
can melt about 20 mr through his passive, has 30 magic penetration with items like 
for a total mr mitigation of 50. His opponent has 40 mr. Therefore Amumu's attacks will deal bonus damage because he melts 10 more mr than his opponent's mr. Its possible to do the same with armor, too. The bonus damage used to be in the form of true damage determined by another formula.
I'll sometimes go all in on melting magic resistances on Amumu by adding 
and 
. Its a squishier build but its deadly to Carries. Its roughly equivalent to 75 magic penetration.
So its possible through specific builds to increase the amount of damage you dish out.
Zane Zephyr1 votesIt's actually not true damage, you're just taking 100% of the total possible damage of the ability
