Huh. Always remembered it being +25% damage... Testing this now, and this possibly warrants a bug, since slardar with some massive -armor items, along with a dazzle, could destroy even PL with high armor exceedingly fast. Also going to see what the max damage amplification by unnatural means is, since the HIGHEST possible by one team alone is <-80.

Ok, here it is.

Damage with 8% resistance

Damage with 38% resistance

Maximum Amplification, about -800 armor, -97%. I've been hitting at about this point from now on.

Hit w/o MoM at -97% resistance

and then with.

Using D*Crit*amp*MoM amp, which is 1926*4*1.97*1.3, and substituting/giving when needed.

8% resist(.92 amplification)=7087.68 Very close to what is seen. No issues there.

38% resist(.62 amplification)=4776.48 Also extremely close

-97% resistance(1.97 amp)=15176.88 just under the 15220 seen.

-97% resist with MoM amp=19729.944 also just under the amount seen.

I think the damage amplification from -armor doesn't exist, nor is the exponential calculation of it correct.