I’m not sure armor/reality formula has been revealed already, but I did some calculations and I figure it out. Hope it helps!

*Please note that I did this research on my own and the data I’ve collected is not official, so the formula may not be correct.

First, let me tell you something that I found surprising. The armor/reality’s damage reduction is affected by the hero’s HP; the higher the ratio of the armor/reality to the HP is, the more the damage is reduced. In other words, a hero with lower HP takes less damage than a hero with higher HP when they have the same amount of armor/reality.

Here is the formula:

HP ÷ (HP + armor ×10) × 100 = percent of normal damage the hero takes

You can do the same thing for fantastic damage by putting ‘reality’ instead of ‘armor’.

So, a hero with 100k HP and 15k armor takes about 60% less damage to the attacker’s original damage, calculated by the formula, 100000 ÷ (100000 + 150000) × 100= 40.